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contract, a set of promises agreed to in a \"meeting of the minds\", is the traditional way to formalize a relationship. While contracts are primarily used in business relationships (the focus of this article), they can also involve personal relationships such as marraiges. Contracts are also important in politics, not only because of \"social contract\" theories but also because contract enforcement has traditionally been considered a basic function of capitalist governments.",{"_31":835,"_33":836},[],{"_35":160,"_37":837,"_39":447,"_41":838,"_66":839,"_68":847,"_70":69},"5E4zoIt_",{},[840],{"_35":204,"_167":841,"_169":843,"_41":845,"_70":846},[842],253,[844],284,{},"https://www.fon.hum.uva.nl/rob/Courses/InformationInSpeech/CDROM/Literature/LOTwinterschool2006/szabo.best.vwh.net/kolmogorov.html","Whether enforced by a government, or otherwise, the contract is the basic building block of a free market economy. Over many centuries of cultural evolution has emerged both the concept of contract and principles related to it, encoded into common law. Algorithmic information theory suggests that such evolved structures are often prohibitively costly to recompute. If we started from scratch, using reason and experience, it could take many centuries to redevelop sophisticated ideas like property rights that make the modern free market work [Hayek].",{"_31":849,"_33":850},[],{"_35":160,"_37":851,"_39":447,"_41":852,"_66":853,"_68":854,"_70":69},"AO3IFkep",{},[],"The success of the common law of contracts, combined with the high cost of replacing it, makes it worthwhile to both preserve and to make use of these principles where appropriate. Yet, the digital revolution is radically changing the kinds of relationships we can have. What parts of our hard-won legal tradition will still be valuable in the cyberspace era? What is the best way to apply these common law principles to the design of our on-line relationships?",{"_31":856,"_33":857},[],{"_35":160,"_37":858,"_39":447,"_41":859,"_66":860,"_68":861,"_70":69},"P-gR_HSR",{},[],"Computers make possible the running of algorithms heretofore prohibitively costly, and networks the quicker transmission of larger and more sophsiticated messages. Furthermore, computer scientists and cryptographers have recently discovered many new and quite interesting algorithms. Combining these messages and algorithms makes possible a wide variety of new protocols.",{"_31":863,"_33":864},[],{"_35":160,"_37":865,"_39":447,"_41":866,"_66":867,"_68":868,"_70":69},"FDIEBT0K",{},[],"New institutions, and new ways to formalize the relationships that make up these institutions, are now made possible by the digital revolution. I call these new contracts \"smart\", because they are far more functional than their inanimate paper-based ancestors. No use of artificial intelligence is implied. A smart contract is a set of promises, specified in digital form, including protocols within which the parties perform on these promises.",{"_35":870,"_37":871,"_39":447,"_41":872,"_66":873,"_68":874,"_70":69},"Heading","8RDRtJT7",{"_273":323},[],"Introduction",{"_31":876,"_33":891},[877,884],{"_31":878,"_33":879},[],{"_35":160,"_37":880,"_39":447,"_41":881,"_66":882,"_68":883,"_70":69},"wAS9Xqqs",{},[],"The basic idea of smart contracts is that many kinds of contractual clauses (such as liens, bonding, delineation of property rights, etc.) can be embedded in the hardware and software we deal with, in such a way as to make breach of contract expensive (if desired, sometimes prohibitively so) for the breacher. A canonical real-life example, which we might consider to be the primitive ancestor of smart contracts, is the humble vending machine. Within a limited amount of potential loss (the amount in the till should be less than the cost of breaching the mechanism), the machine takes in coins, and via a simple mechanism, which makes a beginner's level problem in design with finite automata, dispense change and product fairly. Smart contracts go beyond the vending machine in proposing to embed contracts in all sorts of property that is valuable and controlled by digital means. Smart contracts reference that property in a dynamic, proactively enforced form, and provide much better observation and verification where proactive measures must fall short. And where the vending machine, like electronic mail, implements an asynchronous protocol between the vending company and the customer, some smart contracts entail multiple synchronous steps between two or more parties.",{"_31":885,"_33":886},[],{"_35":160,"_37":887,"_39":447,"_41":888,"_66":889,"_68":890,"_70":69},"BZ2iU4-N",{},[],"Other forerunners of smart contracts include POS (Point of Sale) terminals and cards, EDI (Electronic Data Interchange, used for ordering and other transactionsbetween large corporations), and the SWIFT, ACH, and FedWire networks for transferring and clearing payments between banks. These implement commercial security models, but too often with little heed paid to the contractual needs and obligations of the parties.",{"_35":870,"_37":892,"_39":447,"_41":893,"_66":894,"_68":895,"_70":69},"sKrmBcRD",{"_273":323},[],"Contracts Embedded in the World",{"_31":897,"_33":939},[898,926],{"_31":899,"_33":914},[900,907],{"_31":901,"_33":902},[],{"_35":160,"_37":903,"_39":447,"_41":904,"_66":905,"_68":906,"_70":69},"G5rPLoVx",{},[],"(a) robust against naive vandalism, and",{"_31":908,"_33":909},[],{"_35":160,"_37":910,"_39":447,"_41":911,"_66":912,"_68":913,"_70":69},"ojBrxvz-",{},[],"(b) robust against sophisticated, incentive compatible (rational) breach",{"_35":160,"_37":915,"_39":447,"_41":916,"_66":917,"_68":925,"_70":69},"cPuJ0mza",{"_273":323},[918],{"_35":919,"_167":920,"_169":922,"_41":924,"_70":69},"Italic",[921],95,[923],116,{},"A broad statement of the key idea of smart contracts, then, is to say that contracts should be embedded in the world. The mechanisms of the world should be structured in such a way as to make the contracts",{"_31":927,"_33":928},[],{"_35":160,"_37":929,"_39":447,"_41":930,"_66":931,"_68":938,"_70":69},"yIxHfsxW",{},[932],{"_35":204,"_167":933,"_169":935,"_41":937,"_70":846},[934],859,[936],889,{},"A vandal can be a strategy or sub-strategy of a game whose utility is at least partially a function of one's own negative utility; or it can be a mistake by a contracting party to the same effect. \"Naive\" simply refers to both lack of forethought as to the consequences of a breach, as well as the relatively low amount of resources expended to enable that breach. Naive vandalism is common enough that it must be taken into consideration. A third category, (c) sophisticated vandalism (where the vandals can and are willing to sacrifice substantial resources), for example a military attack by third parties, is of a special and difficult kind that doesn't often arise in typical contracting, so that we can place it in a separate category and ignore it here. The distinction between naive and sophisticated strategies has been computationally formalized in algorithmic information theory",{"_35":870,"_37":940,"_39":447,"_41":941,"_66":942,"_68":943,"_70":69},"6faQBhSe",{"_273":323},[],"Attacks against Smart Contracts",{"_31":945,"_33":1043},[946,965,977,990,1003,1016,1023,1036],{"_31":947,"_33":948},[],{"_35":160,"_37":949,"_39":447,"_41":950,"_66":951,"_68":964,"_70":69},"E6G1Y7Pw",{},[952],{"_35":919,"_167":953,"_169":958,"_41":963,"_70":69},[954,955,956,957],286,423,568,711,[959,960,961,962],294,433,579,720,{},"The threat of physical force is an obvious way to embed a contract in the world -- have a judicial system decide what physical steps are to be taken out by an enforcement agency (including arrest, confiscation of property, etc.) in response to a breach of contract. It is what I call a reactive form of security. The need to invoke reactive security can be minimized, but not eliminated, by making contractual arrangements verifiable, for example by recording a breach on a video camera, or putting a signature on a contract, in order to prove breach claims in court. Observation of a contract in progress, in order to detect the first sign of breach and minimize losses, also is a reactive form of security. A proactive form of security is a physical mechanism that makes breach expensive, such as a combination lock that makes access to a room containing trade secrets expensive without explicit authorization.",{"_31":966,"_33":967},[],{"_35":160,"_37":968,"_39":447,"_41":969,"_66":970,"_68":976,"_70":69},"ZLSxqFCz",{},[971],{"_35":919,"_167":972,"_169":974,"_41":975,"_70":69},[973],165,[186],{},"From common law, economic theory, and contractual conditions often found in practice, we can distill four basic objectives of contract design. The first of these is observability, the ability of the principals to observe each others' performance of the contract, or to prove their performance to other principals. The field of accounting is, roughly speaking, primarily concerned with making contracts an organization is involved in more observable.",{"_31":978,"_33":979},[],{"_35":160,"_37":980,"_39":447,"_41":981,"_66":982,"_68":989,"_70":69},"zXNQqDxK",{},[983],{"_35":919,"_167":984,"_169":986,"_41":988,"_70":69},[985],19,[987],32,{},"A second objective verifiability, the ability of a principal to prove to an arbitrator that a contract has been performed or breached, or the ability of the arbitrator to find this out by other means. The disciplines of auditing and investigation roughly correspond with verification of contract performance. Observability and verifiability can also include the ability to differentiate between intentional violations of the contract and good faith errors.",{"_31":991,"_33":992},[],{"_35":160,"_37":993,"_39":447,"_41":994,"_66":995,"_68":1002,"_70":69},"kmasqf03",{},[996],{"_35":919,"_167":997,"_169":999,"_41":1001,"_70":69},[998],40,[1000],47,{},"A third objective of contract design is privity, the principle that knowledge and control over the contents and performance of a contract should be distributed among parties only as much as is necessary for the performance of that contract. This is a generalization of the common law principle of contract privity, which states that third parties, other than the designated arbitrators and intermediaries, should have no say in the enforcement of a contract. Generalized privity goes beyond this to formalize the common claim, \"it's none of your business\". Attacks against privity are epitomized by third parties Eve the eavesdropper, a passive observer of contents or performance, and malicious Mallet, who actively interferes with performance or steals service. Under this model privacy and confidentiality, or protecting the value of information about a contract, its parties, and its performance from Eve, is subsumed under privity, as are property rights. The field of security (especially, for smart contracts, computer and network security), roughly corresponds to the goal of privity.",{"_31":1004,"_33":1005},[],{"_35":160,"_37":1006,"_39":447,"_41":1007,"_66":1008,"_68":1015,"_70":69},"fdJ00b-P",{},[1009],{"_35":919,"_167":1010,"_169":1012,"_41":1014,"_70":69},[1011],22,[1013],36,{},"A fourth objective is enforceability, and at the same time minimizing the need for enforcement. Improved verifiability often also helps meet this fourth objective. Reputation, built-in incentives, \"self-enforcing\" protocols, and verifiability can all play a strong part in meeting the fourth objective. Computer and network security also can contribute greatly to making smart contracts self-enforcing.",{"_31":1017,"_33":1018},[],{"_35":160,"_37":1019,"_39":447,"_41":1020,"_66":1021,"_68":1022,"_70":69},"kgYDWybt",{},[],"Smart contracts often involve trusted third parties, exemplified by an intermediary, who is involved in the performance, and an arbitrator, who is invoked to resolve disputes arising out of performance (or lack thereof). Privity implies that we want to minimize vulnerability to third parties. Verifiability and observabiliy often require that we invoke them. A mediator must be trusted with some of the contents and/or performance of the contract. An arbitrator must be trusted with some of the contents, and some of the history of performance, and to resolve disputes and invoke penalties fairly. In smart contract design we want to get the most out of intermediaries and arbitrators, while minimizing exposure to them. One common outcome is that confidentiality is violated only in case of dispute.",{"_31":1024,"_33":1025},[],{"_35":160,"_37":1026,"_39":447,"_41":1027,"_66":1028,"_68":1035,"_70":69},"2e3GxHik",{},[1029],{"_35":204,"_167":1030,"_169":1031,"_41":1033,"_70":1034},[923],[1032],145,{},"https://www.fon.hum.uva.nl/rob/Courses/InformationInSpeech/CDROM/Literature/LOTwinterschool2006/szabo.best.vwh.net/multi.small.html","In the future the size distribution of multinational companies will approach that of local business, giving rise to multinational small business . Legal barriers are the most severe cost of doing business across many jurisdictions. Smart contracts can cut through this Gordian knot of jurisdictions. Where smart contracts can increase privity, they can decrease vulnerability to capricious jurisdictions. Where smart contracts can increase observability or verifiability, they can decrease dependence on these obscure local legal codes and enforcement traditions.",{"_31":1037,"_33":1038},[],{"_35":160,"_37":1039,"_39":447,"_41":1040,"_66":1041,"_68":1042,"_70":69},"1khT36kZ",{},[],"The consequences of smart contract design on contract law and economics, and on strategic contract drafting, (and vice versa), have been little explored. As well, I suspect the possibilities for greatly reducing the transaction costs of executing some kinds of contracts, and the opportunities for creating new kinds of businesses and social institutions based on smart contracts, are vast but little explored. The \"cypherpunks\" have explored the political impact of some of the new protocol building blocks. The field of Electronic Data Interchange (EDI), in which elements of traditional business transactions (invoices, receipts, etc.) are exchanged electronically, sometimes including encryption and digital signature capabilities, can be viewed as a primitive forerunner to smart contracts. Indeed those business forms can provide good starting points and channel markers for smart contract designers.",{"_35":870,"_37":1044,"_39":447,"_41":1045,"_66":1046,"_68":1047,"_70":69},"yDbqeOMM",{"_273":323},[],"Some Basic Principles of Contract Design",{"_31":1049,"_33":1064},[1050,1057],{"_31":1051,"_33":1052},[],{"_35":160,"_37":1053,"_39":447,"_41":1054,"_66":1055,"_68":1056,"_70":69},"H0WLXiNl",{},[],"One important task of smart contracts, that has been largely overlooked by traditional EDI, is critical to \"the meeting of the minds\" that is at the heart of a contract: communicating the semantics of the protocols to the parties involved. There is ample opportunity in smart contracts for \"smart fine print\": actions taken by the software hidden from a party to the transaction. For example, grocery store POS machines don't tell customers whether or not their names are being linked to their purchases in a database. The clerks don't even know, and they've processed thousands of such transactions under their noses. Thus, via hidden action of the software, the customer is giving away information they might consider valuable or confidential, but the contract has been drafted, and transaction has been designed, in such a way as to hide those important parts of that transaction from the customer.",{"_31":1058,"_33":1059},[],{"_35":160,"_37":1060,"_39":447,"_41":1061,"_66":1062,"_68":1063,"_70":69},"aBQBg2EY",{},[],"To properly communicate transaction semantics, we need good visual metaphors for the elements of the contract. These would hide the details of the protocol without surrendering control over the knowledge and execution of contract terms. A primitive but good example is provided by the SecureMosiac software from CommerceNet. Encryption is shown by putting the document in an envelope, and a digital signature by affixing a seal onto the document or envelope. On the other hand, Mosaic servers log connections, and sometimes even transactions, without warning users -- classic hidden actions.",{"_35":870,"_37":1065,"_39":447,"_41":1066,"_66":1067,"_68":1068,"_70":69},"1bqx2PGw",{"_273":323},[],"Observability & Hidden Actions",{"_31":1070,"_33":1182},[1071,1086,1108,1120,1139,1150,1163],{"_31":1072,"_33":1073},[],{"_35":160,"_37":1074,"_39":447,"_41":1075,"_66":1076,"_68":1085,"_70":69},"6eNVwDGR",{},[1077],{"_35":919,"_167":1078,"_169":1081,"_41":1084,"_70":69},[1079,1080],39,356,[1082,1083],62,360,{},"Protocols based on mathematics, called cryptographic protocols, tre the basic building blocks that implement the improved tradeoffs between observability, verifiability, privity, and enforceability in smart contracts. Contrary to the common wisdom, obscurity is often critical to security. Cryptographic protocols are built around foci of obscurity called keys. A key's immense unknown randomness allows the rest of the system to be simple and public. The obscurity of a large random number, so vast that a lucky guess is unlikely in in, if desired, the lifetime of the universe, is the foundation upon which cryptographic protocols, and in turn smart contracts, are built.",{"_31":1087,"_33":1088},[],{"_35":160,"_37":1089,"_39":447,"_41":1090,"_66":1091,"_68":1107,"_70":69},"lnFqFC19",{},[1092,1100],{"_35":919,"_167":1093,"_169":1096,"_41":1099,"_70":69},[1094,1095],120,380,[1097,1098],130,391,{},{"_35":204,"_167":1101,"_169":1103,"_41":1105,"_70":1106},[1102],1002,[1104],1005,{},"http://szabo.best.vwh.net/rsa.html","A wide variety of new cryptographic protocols have emerged in recent years. The most tradtional kind of cryptography is secret key cryptography, in which Alice and Bob (our exemplar parties to a smart contract) use a single shared, prearranged key to encrypt messages between them. A fundamental problem we will see throughout these protocols is the need to keep keys secret, and pubilic key cryptography helps solve this. In this technique, Alice generates two keys, called the private and public keys. She keeps the private key secret and well protected, and publishes the public key. When Bob wishes to send a message to Alice, he encrypts a message with her public key, sends the encrypted message, and she decrypts the message with her private key. The private key provides a \"trapdoor\" that allows Alice to compute an easy inverse of the encryption function that used the public key. The public key provides no clue as to what the private key is, even though they are mathematically related. The RSA algorithm is the most widely used method of public key cryptography.",{"_31":1109,"_33":1110},[],{"_35":160,"_37":1111,"_39":447,"_41":1112,"_66":1113,"_68":1119,"_70":69},"x8HfPaye",{},[1114],{"_35":919,"_167":1115,"_169":1116,"_41":1118,"_70":69},[1082],[1117],80,{},"Public key cryptography also makes possible a wide variety of digital signatures. These proves that a piece of data (hereafter referred to as just an \"object\") was in active contact with the private key corresponding to the signature: the object was actively \"signed\" with that key. The digital signature probably should have been called a \"digital stamp\" or \"digital seal\" since its function resembles more those methods than an autograph. In particular, it is not biometric like an autograph, although incorporation of a typed-in password as part of the private key used to sign can sometimes subsitute for an autograph. In many Asian countries, a hand-carved wooden block, called a \"chop\", is often used instead of autographs. Every chop is unique, and because of the unique carving and wood grain cannot be copied. A digital signature is similar to the chop, since every newly generated key is unique, but it is trivial to copy the key if obtained from the holder. A digital signature relies on the assumption that the holder will keep the private key secret.",{"_31":1121,"_33":1122},[],{"_35":160,"_37":1123,"_39":447,"_41":1124,"_66":1125,"_68":1138,"_70":69},"84LIsRBE",{},[1126,1131],{"_35":919,"_167":1127,"_169":1128,"_41":1130,"_70":69},[16],[1129],17,{},{"_35":204,"_167":1132,"_169":1134,"_41":1136,"_70":1137},[1133],589,[1135],609,{},"http://www.digicash.com/publish/bigbro.html","A blind signature is a digital signature and secret-key encryption protocol that together have the mathematical property of commutativity, so that they can be stripped in reverse of the order they were applied. The effect is that Bob \"signs\" an object, for which he can verify its general form, but cannot see its specific content. Typically the key of the signature defines the meaning of the signed object, rather than the contents of the object signed, so that Bob doesn't sign a blank check. Blind signatures used in digital bearer instruments, where Bob is the clearing agent, and in Chaumian credentials , where Bob is the credential issuer.",{"_31":1140,"_33":1141},[],{"_35":160,"_37":1142,"_39":447,"_41":1143,"_66":1144,"_68":1149,"_70":69},"dl-ils-N",{},[1145],{"_35":919,"_167":1146,"_169":1147,"_41":1148,"_70":69},[137],[171],{},"Secret sharing is a method of splitting a key (and thus control over any object encrypted with that key) into N parts, of which only M are needed to recreate the key, but less than M of the parts provide no information about the key. Secret sharing is a potent tool for distributing control over objects between principals.",{"_31":1151,"_33":1152},[],{"_35":160,"_37":1153,"_39":447,"_41":1154,"_66":1155,"_68":1162,"_70":69},"4mmQju8P",{},[1156],{"_35":204,"_167":1157,"_169":1159,"_41":1160,"_70":1161},[1158],4,[1013],{},"http://www.niksula.cs.hut.fi/~haa/nonpub/zeroknowledge.html","The zero-knowledge interactive proof is an alternative to public key methods for challenge-response identification. Otherwise normally functioning parties who have an incentive to respond properly to the challenge, but fail to do so, do not possess the key), without revealing any information about that privatge key to the challenger or any eavesdroppers. ZKIPs are currently used for authentication, and in smart weapons for Identification Friend or Foe (IFF).",{"_31":1164,"_33":1165},[],{"_35":160,"_37":1166,"_39":447,"_41":1167,"_66":1168,"_68":1181,"_70":69},"qyW9d3MJ",{},[1169,1175],{"_35":204,"_167":1170,"_169":1172,"_41":1174,"_70":1137},[1171],226,[1173],246,{},{"_35":919,"_167":1176,"_169":1178,"_41":1180,"_70":69},[1177],361,[1179],372,{},"Information about who is talking to whom, such as can be found on telephone bills, can be quite valuable even without records of the actual content. Confidential messsaging is necessary for the some of the privity features of Chaumian credentials and bearer securities to be strongly implemented on an actual network. To provide this traffic confidentiality, a digital mix can allow parties to communicate across a network without revealing their partners to network providers or the outside world. In a mix, traffic analysis by Eve is prevented by the Russian-doll encryption of the message by the sender with the public keys of each mix operator in the chain, and the mixing of messages by each operator, so that panoptic wiretapper Eve loses track of the messages. For the sender/recipient pair to remain confidential, only 1 out of N of the operators needs to be trusted with their local traffic information, although Eve can sometimes gather statistics over large numbers of messages between the same partners to eventually guess who is talking to whom. The communicating parties can also be mutually anonymous, and with normal encryption need trust no other parties with the content of messages. The \"Mixmaster\" software on the Internet implements most of the features of a digital mix[Mixmaster].",{"_35":870,"_37":1183,"_39":447,"_41":1184,"_66":1185,"_68":1186,"_70":69},"fEoK8lyx",{"_273":323},[],"Cryptographic Building Blocks",{"_31":1188,"_33":1224},[1189,1196,1203,1210,1217],{"_31":1190,"_33":1191},[],{"_35":160,"_37":1192,"_39":447,"_41":1193,"_66":1194,"_68":1195,"_70":69},"MNhDzNt0",{},[],"So far, we've assumed parties like Alice and Bob are monolithic. But in the world of smart contracts, they will use computer-based software agents and smart cards to do their electronic bidding. Keys are not necessarily tied to identities, and the task of doing such binding turns out to be more difficult than at first glance. Once keys are bound, they need to be well protected, but wide area network connections are notoriously to hacking.",{"_31":1197,"_33":1198},[],{"_35":160,"_37":1199,"_39":447,"_41":1200,"_66":1201,"_68":1202,"_70":69},"8mI4_IaB",{},[],"If we assume that the attacker has the ability to intercept and redirect any messages in the network protocol, as is the case on wide area netowrks such as the Internet. then we must also assume, for practical all commercial operating systems, that they would also be able to invade client if not merchant computers and find any keys lying on the disk.",{"_31":1204,"_33":1205},[],{"_35":160,"_37":1206,"_39":447,"_41":1207,"_66":1208,"_68":1209,"_70":69},"1Wv7NXUV",{},[],"There's no completely satisfactory solution to end point operations security from network-based attacks, but here's a strategy for practically defanging this problem for public-key based systems:",{"_31":1211,"_33":1212},[],{"_35":160,"_37":1213,"_39":447,"_41":1214,"_66":1215,"_68":1216,"_70":69},"oQ6orEAm",{},[],"All public key operation are are done inside an unreadable hardware board on a machine with a very narrow serial-line connection (ie, it carries only a simple single-use protocol with well-verified security) to a dedicated firewall. Such a board is available, for example, from Kryptor, and I believe Viacrypt may also have a PGP-compatable board. This is economical for central sites, but may be less practical for normal users. Besides better security, it has the added advantage that hardware speeds up the public key computations.",{"_31":1218,"_33":1219},[],{"_35":160,"_37":1220,"_39":447,"_41":1221,"_66":1222,"_68":1223,"_70":69},"N0PaM2gx",{},[],"If Mallet's capability is to physically sieze the machine, a weaker form of key protection will suffice. The trick is to hold the keys in volatile memory. This makes the PC proof from physical attacks -- all that needed to destroy the keys is to turn off the PC. If the key backups can be hidden in a different, secure physical location, this allows the user of this PC to encrypt large amounts of data both on the PC itself and on public computer networks, without fear that physical attack against the PC will compromise that data. The data is still vulnerable to a \"rubber hose attack\" where the owner is coerced into revealing the hidden keys. Protection against rubber hose attacks might require some form of Shamir secret sharing which splits the keys between diverse phgsical sites.",{"_35":870,"_37":1225,"_39":447,"_41":1226,"_66":1227,"_68":1228,"_70":69},"vYetqqhS",{"_273":323},[],"Protection of Keys",{"_31":1230,"_33":1328},[1231,1238,1251],{"_31":1232,"_33":1233},[],{"_35":160,"_37":1234,"_39":447,"_41":1235,"_66":1236,"_68":1237,"_70":69},"A5nCaV9L",{},[],"How does Alice know she has Bob's key? Who, indeed, can be the parties to a smart contract? Can they be defined just by their keys? Do we need biometrics (such as autographs, typed-in passwords, retina scans, etc.)?",{"_31":1239,"_33":1240},[],{"_35":160,"_37":1241,"_39":447,"_41":1242,"_66":1243,"_68":1250,"_70":69},"56UzyDzm",{},[1244],{"_35":919,"_167":1245,"_169":1247,"_41":1249,"_70":69},[1246],127,[1248],138,{},"The public key cryptography software package \"Pretty Good Privacy\" (PGP) uses a model called \"the web of trust\". Alice chooses introducers whom she trusts to properly identify the map between other people and their public keys. PGP takes it from there, automatically validating any other keys that have been signed by Alice's designated introducers.",{"_31":1252,"_33":1323},[1253,1260,1281],{"_31":1254,"_33":1255},[],{"_35":160,"_37":1256,"_39":447,"_41":1257,"_66":1258,"_68":1259,"_70":69},"uKFzqaxs",{},[],"1) Does the key actually belong to whom it appears to belong? In other words, has it been certified with a trusted signature?",{"_31":1261,"_33":1276},[1262,1269],{"_31":1263,"_33":1264},[],{"_35":160,"_37":1265,"_39":447,"_41":1266,"_66":1267,"_68":1268,"_70":69},"GDX3ULZm",{},[],"Having been told by Alice the answer to the second question, PGP can calculates the answer to the first question for the public keys Alice has collected.",{"_31":1270,"_33":1271},[],{"_35":160,"_37":1272,"_39":447,"_41":1273,"_66":1274,"_68":1275,"_70":69},"eT4Ugg4D",{},[],"Keys that have been certified by a trusted introducer are deemed valid by PGP. The keys belonging to trusted introducers must themselves be certified either by you or by other trusted introducers. This \"transitivity\" introduces an implicit third criterion",{"_35":160,"_37":1277,"_39":447,"_41":1278,"_66":1279,"_68":1280,"_70":69},"bIUzOUmz",{"_273":323},[],"2) Does it belong to an introducers, someone you can trust to certify other keys?",{"_31":1282,"_33":1318},[1283,1290,1297,1304,1311],{"_31":1284,"_33":1285},[],{"_35":160,"_37":1286,"_39":447,"_41":1287,"_66":1288,"_68":1289,"_70":69},"1MbR_oFn",{},[],"PGP confuses this with criterion (2). It is not clear that any single person has enough judgement to properly undertake task (3), nor has a reasonable institution been proposed that will do so. This is one of the unsolved problems in smart contracts.",{"_31":1291,"_33":1292},[],{"_35":160,"_37":1293,"_39":447,"_41":1294,"_66":1295,"_68":1296,"_70":69},"YuiU4TH5",{},[],"PGP also can be given trust ratings and programmed to compute a weighted score of validity-- for example, two marginally trusted signatures might be considered as credible as one fully trusted signature.",{"_31":1298,"_33":1299},[],{"_35":160,"_37":1300,"_39":447,"_41":1301,"_66":1302,"_68":1303,"_70":69},"0VRUzXL8",{},[],"Any keys in Alice's secret key ring are \"axiomatically\" valid to Alice's PGP program, needing no introducer's signature. PGP also assumes that Alice ultimately trusts herself to certify other keys.",{"_31":1305,"_33":1306},[],{"_35":160,"_37":1307,"_39":447,"_41":1308,"_66":1309,"_68":1310,"_70":69},"yWXWyqa3",{},[],"It is believed that PGP causes the emergence of a decentralized fault-tolerant web of confidence for all public keys, but a chain of introduced introducers grows weak very quickly, due to lack of transitivity.",{"_31":1312,"_33":1313},[],{"_35":160,"_37":1314,"_39":447,"_41":1315,"_66":1316,"_68":1317,"_70":69},"r7ftrFLc",{},[],"PGP's grass-roots approach contrasts sharply with tradtional public key management schemes, such as X.509 and the related Privacy Enhanced Mail (PEM). These standard schemes subsistute a heirarchical system of introducers called certification authorities (CAs).",{"_35":160,"_37":1319,"_39":447,"_41":1320,"_66":1321,"_68":1322,"_70":69},"95cRZm6a",{"_273":323},[],"3) Does the key belong to someone you can trust to introduce other introducers?",{"_35":160,"_37":1324,"_39":447,"_41":1325,"_66":1326,"_68":1327,"_70":69},"3Uyvggp-",{"_273":323},[],"There are two entirely separate criteria PGP uses to judge a public key's usefulness:",{"_35":870,"_37":1329,"_39":447,"_41":1330,"_66":1331,"_68":1332,"_70":69},"w14MGSFB",{"_273":323},[],"The Man In the Middle & PGP's Web of Trust",{"_31":1334,"_33":1356},[1335,1342,1349],{"_31":1336,"_33":1337},[],{"_35":160,"_37":1338,"_39":447,"_41":1339,"_66":1340,"_68":1341,"_70":69},"1H3pwELJ",{},[],"Two different acts are often called \"notarization\". The first is simply where one swears to the truth of some affidavit before a notary or some other officer entitled to take oaths. This does not require the notary to know who the affiant is. The second act is when someone \"acknowledges\" before a notary that he has executed a document as ``his own act and deed.'' This second act requires the notary to know the person making the acknowledgment. Thus, for example, the form of an acknowledgment can go something like this:",{"_31":1343,"_33":1344},[],{"_35":160,"_37":1345,"_39":447,"_41":1346,"_66":1347,"_68":1348,"_70":69},"uK2zOldQ",{},[],"On this ____ day of ___, 19__, personally appeared before me ____, known to me and known to me to be the person who signed the foregoing instrument, and acknowledged that he executed the same as his own act and deed.",{"_31":1350,"_33":1351},[],{"_35":160,"_37":1352,"_39":447,"_41":1353,"_66":1354,"_68":1355,"_70":69},"iqq8puOX",{},[],"In the first type of act of notarization, the notary merely certifies that the affiant swore the statement was true. In the second type the notary actually vouches that the person making the acknowledgment was who he claims to be.",{"_35":870,"_37":1357,"_39":447,"_41":1358,"_66":1359,"_68":1360,"_70":69},"dyvRlJNe",{"_273":323},[],"Notaries Public",{"_31":1362,"_33":1424},[1363,1376,1383,1390,1397,1404,1417],{"_31":1364,"_33":1365},[],{"_35":160,"_37":1366,"_39":447,"_41":1367,"_66":1368,"_68":1375,"_70":69},"GyWiypqN",{},[1369],{"_35":919,"_167":1370,"_169":1372,"_41":1374,"_70":69},[1371],289,[1373],317,{},"These roles of a notary public are substantially different from the alleged role of heirarchies of \"certification authorities\" (CAs) in PEM/X.509, and the \"web of trust\" in PGP, to \"prove identity\". In fact the certificates generated by these systems do no such thing. Rather a certficate proves that a claim was made by a CA at some time in the past. The (implicit) claim is that a particular key belonged to a particular person at that time. That key is not biometric like an autograph, and can thus be transferred at any time. Furthermore, false claims can be made by a CA about what keys an end-user has held, and the end-user can be stuck with no evidence of CA fraud; nor does the CA have any way of proving that their claim is correct if an end-user challenges it. It is extremely difficult, on the other hand, for notary publics to forge autographs and expect to get away with it often enough to maintain their professional reputations.",{"_31":1377,"_33":1378},[],{"_35":160,"_37":1379,"_39":447,"_41":1380,"_66":1381,"_68":1382,"_70":69},"7A4HSU84",{},[],"Both the PGP web of trust and X.509 models suffer from more flaws. A single rooted heirarchy assumes a mythological beast called a universally trusted entity. Heirarchies in general create rigid structures that don't fit the way knowledge about keys and keyholders, and incentives to accurately reflect that knowledge, are distributed among people in the real world. In turn, hile PGP distinguishes between \"Alice holds a key\" and \"Alice can be trusted to certify a key\", it does not follow that the second claim that Alice can be trusted to validate another issuer. There is little transitivity: seeing Alice's key certified by Bob, whom I know and trust, tells me little about whether Alice's certification of Charlie's key is correct. Seeing Alice certified by Bob as an introducer tells me little about wether Alice can be trusted to certify other introducers. It does tell me that I know to blame Alice if her claim turns out to be wrong; although it's far from clear that Alice has any legal liability.",{"_31":1384,"_33":1385},[],{"_35":160,"_37":1386,"_39":447,"_41":1387,"_66":1388,"_68":1389,"_70":69},"9WMZZlNL",{},[],"There is an even more severe flaw when public key is used for digital signatures. Because the claim was only made in the past, both PGP and X.509 allow the end user to plausible deny that they \"signed\" a document; and conversely if one's key is surreptitiously stolen, or for other reasons no revocation action is taken, there is no way to prove that one did not \"sign\" the documenent digitally \"signed\" with the stolen key. Finally, there is no widely accepted legal agreement on what is specifically being claimed when one \"certifies\" a key, nor is there any built-in or widely used mechanism for describing the actual claim one is making. Real world CAs have a nasty habit of disclaiming liability for their mistakes, or for the misunderstandings that will arise out of the often vague and sloppy, sometimes implicit claims they make. Finally, there are a wide variety of other claims one might make about a key, such as \"this key belongs to an office\", \"this key belongs to a server\", \"this keyholder has a good credit rating\", \"use this key to decrypt your new copy of Microsquish Expel\", \"this key is good for 100 MB of downloads from our web server\", etc. which are facilitated by neither X.509 nor the PGP web of trust.",{"_31":1391,"_33":1392},[],{"_35":160,"_37":1393,"_39":447,"_41":1394,"_66":1395,"_68":1396,"_70":69},"5EWnIQGS",{},[],"We know too little about the best uses of public-key cryptography to establish such fixed methods with such narrow semantics. This author has suggested a mechanism which modifies the PGP web of trust to create arbitrary certificate with a form roughly as follows:",{"_31":1398,"_33":1399},[],{"_35":160,"_37":1400,"_39":447,"_41":1401,"_66":1402,"_68":1403,"_70":69},"Sh9VJjNx",{},[],"Key about which a claim is being made type of claim, in some standard one-line format (like MIME types) Plain text description of claim Timestamp digitally \"signed\", Alice's key",{"_31":1405,"_33":1406},[],{"_35":160,"_37":1407,"_39":447,"_41":1408,"_66":1409,"_68":1416,"_70":69},"b0NbvWcv",{},[1410],{"_35":919,"_167":1411,"_169":1413,"_41":1415,"_70":69},[1412],48,[1414],56,{},"In other words, all claims about keys should be explicit, readily known from reading the certificate itself, and no kind of claim should be arbitrarily excluded by the mechanism. The legal force of the claim can be based on the text itself, rather than overstated, obscure, and often implicit interpretations about what \"certifying\" is supposed to mean. Standard kinds of claims will emerge, including perhaps more transitive \"good judge of judgement\" certificates for which chain-following software can be written, and non-transitive \"is-a-person\" credentials directly \"bound\" to traditional notarized identification by a physical notarization protocol that includes both autographs and digital \"signatures\". More likely, new and more useful kinds of certificates will evolve. These standards should be allowed to emerge out of the wide varieties of possible end uses, much like case law has matured over time, rather than being dictated by our current very inexperienced understanding.",{"_31":1418,"_33":1419},[],{"_35":160,"_37":1420,"_39":447,"_41":1421,"_66":1422,"_68":1423,"_70":69},"tB8CiHqY",{},[],"Meanwhile, there is a more practical defense aggainst the man in the middle attack: advertise, early and often. Users of an insecure network can communicate the integrity of a key reasonably well by tying it to a persistent pattern of behavior: for example posts in a persistent style from a persistent e-mail address, persistence of a key unchallenged on a key server, etc. This is the most practical and widely used way by which PGP users gain confidence in public keys, and it does not require certification authorities or introducers. Those who advertise their keys widely, and those who are well known, are more likely to have keys bound to their person.",{"_35":870,"_37":1425,"_39":447,"_41":1426,"_66":1427,"_68":1428,"_70":69},"BnXTj3bG",{"_273":323},[],"Problems with Certification",{"_31":1430,"_33":1491},[1431,1438,1455,1467,1479],{"_31":1432,"_33":1433},[],{"_35":160,"_37":1434,"_39":447,"_41":1435,"_66":1436,"_68":1437,"_70":69},"9WdTWpwW",{},[],"\"Identity\" is hardly the only thing we might want map to a key. After all, physical keys we use for our house, car, etc. are not necessarily tied to our identity -- we can loan them to trusted friends and relatives, make copies of them, etc. Indeed, in cyberspace we might create \"virtual personae\" to reflect such multi-person relationships, or in contrast to reflect different parts of our personality that we do not want others to link. Here is a possible classification scheme for virtual personae, pedagogically presented:",{"_31":1439,"_33":1440},[],{"_35":160,"_37":1441,"_39":447,"_41":1442,"_66":1443,"_68":1454,"_70":69},"ET_L9ntc",{},[1444,1448],{"_35":919,"_167":1445,"_169":1446,"_41":1447,"_70":69},[16],[201],{},{"_35":204,"_167":1449,"_169":1451,"_41":1453,"_70":1137},[1450],461,[1452],481,{},"A nym is an identifier that links only a small amount of related information about a person, usually that information deemed by the nym holder to be relevant to a particular organization or community. Examples of nyms include electronic bulletin board nicknames, pen names, aliases, and brand names. A nym may gain reputation within its community. For example, a conglomerate may sell a wide variety of brand names, each reputable in its own market niche. With Chaumian credentials , a nym can take advantage of the positive credentials of the holder's other nyms, as provably linked by the is-a-person credential.",{"_31":1456,"_33":1457},[],{"_35":160,"_37":1458,"_39":447,"_41":1459,"_66":1460,"_68":1466,"_70":69},"EmiCJtk2",{},[1461],{"_35":919,"_167":1462,"_169":1463,"_41":1465,"_70":69},[16],[1464],11,{},"A true name is an identifier that links many different kinds of information about an person, such as a full birth name or social security number. As in magick, knowing a true name can confer tremendous power to one's enemies. It also can have major economic value among those who cooperate peacefully, as in the use of direct marketing to target product information to those persons most likely to be interested in those particular products.",{"_31":1468,"_33":1469},[],{"_35":160,"_37":1470,"_39":447,"_41":1471,"_66":1472,"_68":1478,"_70":69},"N1o7Q4ZL",{},[1473],{"_35":919,"_167":1474,"_169":1475,"_41":1477,"_70":69},[16],[1476],9,{},"A persona is any perstient pattern of behavior, along with consistently grouped information such as key(s), name(s), network address(es), writing style, and services provided.",{"_31":1480,"_33":1481},[],{"_35":160,"_37":1482,"_39":447,"_41":1483,"_66":1484,"_68":1490,"_70":69},"6cBbwzaO",{},[1485],{"_35":919,"_167":1486,"_169":1487,"_41":1489,"_70":69},[16],[1488],16,{},"A reputable name is a nym or true name that has a good reputation, usually because it carries many positive credentials, has a good credit rating, or is otherwise highly regarded. Companies strive to carry reputable brand names, while professionals such as doctors and lawyers strive to have many good personal recommendations of their name. Reputable names can be difficult to transfer between parties, because reputation assumes persistence of behavior, but such transfer can sometimes occur (for example, the sale of brand names between companies).",{"_35":870,"_37":1492,"_39":447,"_41":1493,"_66":1494,"_68":1495,"_70":69},"pBMZ0Z5a",{"_273":323},[],"Virtual Personae",{"_31":1497,"_33":1577},[1498,1511,1524,1531,1547,1565],{"_31":1499,"_33":1500},[],{"_35":160,"_37":1501,"_39":447,"_41":1502,"_66":1503,"_68":1510,"_70":69},"-GSV5iVk",{},[1504],{"_35":919,"_167":1505,"_169":1507,"_41":1509,"_70":69},[1506],42,[1508],68,{},"Blind signatures can be used to construct digital bearer instruments, objects identified by a unique key, and issued, cleared, and redeemed by a clearing agent. When an object is transferred, the trasferee can request the clearing agent to verify that the key has never before been cleared, and issue a new key. The clearing agent prevents multiple clearing of particular objects, but can be prevented from linking particular objects one or both of the clearing nyms who transferred that object. These instruments come in an \"online\" variety, cleared during every transfer, and thus both verifiable and observable, and an \"offline\" variety, which can be transfered without being cleared, but is only verifiable when finally cleared, by revealing any the clearing nym of any intermediate holder who transfered the object multiple times (a breach of contract). Privacy from the clearing agent can take the form of transferee-unlinkability, transferer-unlinkability, or \"double blinded\" where both transferer and transferee are unlinkable by the clearing agent.",{"_31":1512,"_33":1513},[],{"_35":160,"_37":1514,"_39":447,"_41":1515,"_66":1516,"_68":1523,"_70":69},"KreozVqm",{},[1517],{"_35":204,"_167":1518,"_169":1519,"_41":1521,"_70":1522},[137],[1520],13,{},"http://www.digicash.com/ecash/about.html","Digital cash is the premier example of a digital bearer instrument, in which the clearing agent is a bank. Bearer instrument protocols enable online payment while honoring the characteristics desired of bearer notes, especially unforgeability (via the clearing mechanism) and transfer confidentiality (via blinding).",{"_31":1525,"_33":1526},[],{"_35":160,"_37":1527,"_39":447,"_41":1528,"_66":1529,"_68":1530,"_70":69},"B6dNwYDO",{},[],"To implement a full transaction of payment for services, we need more than just the digital cash protocol; we need a protocol that guarantees that service will be rendered if payment is made, and vice versa. Current commercial systems use a wide variety of techniques to accomplish this, such as certified mail, face to face exchange, reliance on credit history and collection agencies to extend credit, etc. Smart contracts have the potential to greatly reduce the fraud and enforcement costs of many commercial transactions.",{"_31":1532,"_33":1533},[],{"_35":160,"_37":1534,"_39":447,"_41":1535,"_66":1536,"_68":1546,"_70":69},"x5e3YBgk",{},[1537],{"_35":919,"_167":1538,"_169":1541,"_41":1545,"_70":69},[16,1539,1540],59,217,[1542,1543,1544],12,78,236,{},"A credential is a claim made by one party about another. A positive credential is one the second party would prefer to reveal, such as a degree from a prestigious school, while that party would prefer not to reveal a negative credential such as a bad credit rating.",{"_31":1548,"_33":1549},[],{"_35":160,"_37":1550,"_39":447,"_41":1551,"_66":1552,"_68":1564,"_70":69},"CRAykzp_",{},[1553,1558],{"_35":204,"_167":1554,"_169":1555,"_41":1557,"_70":1137},[16],[1556],21,{},{"_35":919,"_167":1559,"_169":1561,"_41":1563,"_70":69},[1560],185,[1562],207,{},"A Chaumian credential is a cryptographic protocol for proving one possesses claims made about onself by other nyms, without revealing linkages between those nyms. It's based around the is-a-person credential the true name credential, used to prove the linkage of otherwise unlinkable nyms, and to prevent the transfer of nyms between parties.",{"_31":1566,"_33":1567},[],{"_35":160,"_37":1568,"_39":447,"_41":1569,"_66":1570,"_68":1576,"_70":69},"oOOMY43_",{},[1571],{"_35":919,"_167":1572,"_169":1574,"_41":1575,"_70":69},[1573],30,[1000],{},"Another form of credential is bearer credential, a digital bearer instrument where the object is a credential. Here the second party in the claim refers to any bearer -- the claim is tied only to the reputable name of issuing organization, not to the nym or true name of the party holding the credential.",{"_35":870,"_37":1578,"_39":447,"_41":1579,"_66":1580,"_68":1581,"_70":69},"hzuEpbHV",{"_273":323},[],"Constructing Smart Contracts",{"_31":1583,"_33":1672},[1584,1591,1598,1605,1612,1623,1630,1637,1644,1651,1658,1665],{"_31":1585,"_33":1586},[],{"_35":160,"_37":1587,"_39":447,"_41":1588,"_66":1589,"_68":1590,"_70":69},"gd8LFOln",{},[],"We can extend the concept of smart contracts to property. Smart property might be created by embedding smart contracts in physical objects. These embedded protocols would automatically give control of the keys for operating the property to the party who rightfully owns that property, based on the terms of the contract. For example, a car might be rendered inoperable unless the proper challenge-response protocol is completed with its rightful owner, preventing theft. If a loan was taken out to buy that car, and the owner failed to make payments, the smart contract could automatically invoke a lien, which returns control of the car keys to the bank. This \"smart lien\" might be much cheaper and more effective than a repo man. Also needed is a protocol to provably remove the lien when the loan has been paid off, as well as hardship and operational exceptions. For example, it would be rude to revoke operation of the car while it's doing 75 down the freeway.",{"_31":1592,"_33":1593},[],{"_35":160,"_37":1594,"_39":447,"_41":1595,"_66":1596,"_68":1597,"_70":69},"IsaSVL0x",{},[],"Smart property is software or physical devices with the desired characteristics of ownership embedded into them; for example devices that can be rendered of far less value to parties who lack possesion of a key, as demonstrated via a zero knowledge interactive proof.",{"_31":1599,"_33":1600},[],{"_35":160,"_37":1601,"_39":447,"_41":1602,"_66":1603,"_68":1604,"_70":69},"pPKXy1xE",{},[],"One method of implementing smart property is thru operation necessary data (OND): data necessary to the operation of smart property. For example, a complex, OND can be proprietary firing sequence needed to operate a computerized engine, a CAM file needed to manufacture a specialized part, etc. To avoid theft of service, ZKIP is required to open an encrypted channel to the device. To avoid leaking the OND to Eve, tamper detection combined with a dead-man switch can be used on the device end of the channel.",{"_31":1606,"_33":1607},[],{"_35":160,"_37":1608,"_39":447,"_41":1609,"_66":1610,"_68":1611,"_70":69},"hCb4TAZN",{},[],"We might also usedand engrained immobilizing or destructive devices to foil attempts to hot-wire smart property.",{"_31":1613,"_33":1614},[],{"_35":160,"_37":1615,"_39":447,"_41":1616,"_66":1617,"_68":1622,"_70":69},"A7AlEduH",{},[1618],{"_35":919,"_167":1619,"_169":1620,"_41":1621,"_70":69},[16],[1542],{},"A smart lien is the sharing of a smart property between parties, usually two parties called the owner and the lienholder. This property may be in the proximate possesion of the owner or the lienholder, corresponding to the common-law notions of \"artisan's lien\" and \"innkeeper's lien\" respectively. Smart liens might be used to secure lines of credit, insurance policies,and many other kinds of contracts that involve smart property.",{"_31":1624,"_33":1625},[],{"_35":160,"_37":1626,"_39":447,"_41":1627,"_66":1628,"_68":1629,"_70":69},"pnvPCoPI",{},[],"How can debts be collected? No wise bank will lend unless the lendee can either be coerced into repaying the debt, or the loan is more than covered by securely liened collateral plus some conservative function of its reputation for payment in full and on time. For all parties, both credit and liability are closely related, and limited.",{"_31":1631,"_33":1632},[],{"_35":160,"_37":1633,"_39":447,"_41":1634,"_66":1635,"_68":1636,"_70":69},"k9AuCqsv",{},[],"The liability of a party is limited by that party's liens and by the ability to deter that party by threatening punishment for violating contracts (ie, committing crimes as defined by the contract with the jurisdiction). The potential for other actions an party might take that cause liability, such as damage to others' persons or property, also need to be limited. More on that later.",{"_31":1638,"_33":1639},[],{"_35":160,"_37":1640,"_39":447,"_41":1641,"_66":1642,"_68":1643,"_70":69},"Am6gnob0",{},[],"Many parties, especially new entrants, may lack this reputation capital, and will thus need to be able to share their property with the bank via secure liens. A lien is, in a practical sense, a method of sharing a piece of property between the \"owner of record\" and a \"lienholder\", instead of the property having strictly one owner. Liens are used in many large credit transactions, such as auto loans, mortgages, farm loans, etc. They are enforced by the jurisdiction specified in the contract; usually this enforcement is done by the government and subsidized by the taxpayers rather than paid for by the contracting parties. (In fact this usually is the case with contracts and property rights in general, the enforcement clause is an implicit government subsidy). One way to implement a lien without governments is via co-signing with your privately chosen arbitrator (as long as the arbitratror has a good reputation and the contractual right to take appropriate action against you). Smart liens might greatly expand the privity and security of such arrangements.",{"_31":1645,"_33":1646},[],{"_35":160,"_37":1647,"_39":447,"_41":1648,"_66":1649,"_68":1650,"_70":69},"0Mzl3B_h",{},[],"As is the case today, credit problems will usually be solved by artfully written, menacing dunning letters and dings to one's credit rating long before the lien needs to be invoked. However, the lien needs to be enforceable to make these dunning letters credible over the long run.",{"_31":1652,"_33":1653},[],{"_35":160,"_37":1654,"_39":447,"_41":1655,"_66":1656,"_68":1657,"_70":69},"eF2qJr1-",{},[],"What about extending the concept of contract to cover agreement to a prearranged set of tort laws? These tort laws would be defined by contracts between private arbitration and enforcement agencies, while customers would have a choice of jurisdictions in this system of free-market \"governments\". If these privately practiced law organizations (PPLs for short) bear ultimate responsibility for the criminal activities of their customers, or need to insure lack of defection or future payments on the part of customers, they may in turn ask for liens against their customers, either in with contractual terms allowing arrest of customers under certain conditions (eg if they commit acts specified as criminal by the PPL contract) or (more likely for mobile world-traveling and virtual pseudonymous customers) smart liens against liquid assets such as bank accounts and investment portfolios. Smart liens over information, such as digital bearer securities, can be implemented via secret sharing (two or more keys required to unlock the encryption).",{"_31":1659,"_33":1660},[],{"_35":160,"_37":1661,"_39":447,"_41":1662,"_66":1663,"_68":1664,"_70":69},"cSbP6TmN",{},[],"Other important areas of liability include consumer liability and property damage (including pollution). There need to mechanisms so that, for example, pollution damage to others' persons or property can be assessed, and liens should exist so that the polluter can be properly charged and the victims paid. Where pollution is quantifiable, as with SO2 emissions, markets can be set up to trade emission rights. The PPLs would have liens in place to monitor their customer's emissions and assess fees where emission rights have been exceeded.",{"_31":1666,"_33":1667},[],{"_35":160,"_37":1668,"_39":447,"_41":1669,"_66":1670,"_68":1671,"_70":69},"3XXUJvic",{},[],"Alas, there are some dangers where maximum damage could far surpass any liens. A good rule of thumb here is that if the risk is against a third party, and it cannot be liened or insured against, then PPLs should not allow it to be taken. PPLs that allow their customers to take such risks against non-PPL parties would ruin their credit rating. One example of such a risk is building a nuclear plant for which no insurance company is willing to submit liability coverage. If a plant is safe, presumably one should be able to convince a good insurance company to cover its potential to damage others' property.",{"_35":870,"_37":1673,"_39":447,"_41":1674,"_66":1675,"_68":1676,"_70":69},"3Ob8B4a0",{"_273":323},[],"Smart Property",{"_31":1678,"_33":1686},[1679],{"_31":1680,"_33":1681},[],{"_35":160,"_37":1682,"_39":447,"_41":1683,"_66":1684,"_68":1685,"_70":69},"VvgSUb6J",{},[],"Digital cash is here today, and many more smart contract mechanisms are being designed. So far the design criteria important for automating contract execution have come from disparate fields like economics and cryptography, with little cross-communication: little awareness of the technology on the one hand, and little awareness of its best business uses other. The idea of smart contracts is to recognize that these efforts are striving after common objectives, which converge on the concept of smart contracts.",{"_35":870,"_37":1687,"_39":447,"_41":1688,"_66":1689,"_68":1690,"_70":69},"s3u1cYSP",{"_273":323},[],"Conclusion",{"_31":1692,"_33":1693},[],{"_35":160,"_37":1694,"_39":447,"_41":1695,"_66":1696,"_68":1745,"_70":69},"LzfO0b7O",{},[1697,1715,1721,1727,1733,1739],{"_35":919,"_167":1698,"_169":1706,"_41":1714,"_70":69},[987,1699,1700,1701,1702,1703,1704,1705],85,187,219,403,450,492,597,[1707,1708,1709,1710,960,1711,1712,1713],72,171,214,228,468,554,626,{},{"_35":204,"_167":1716,"_169":1717,"_41":1719,"_70":1720},[960],[1718],449,{},"http://www.xmission.com/~legalize/lf/blurbs/f-a-hayek.htm",{"_35":204,"_167":1722,"_169":1724,"_41":1726,"_70":1137},[1723],701,[1725],748,{},{"_35":204,"_167":1728,"_169":1729,"_41":1731,"_70":1732},[1725],[1730],792,{},"http://www.digicash.com/publish/sciam.html",{"_35":204,"_167":1734,"_169":1735,"_41":1737,"_70":1738},[1730],[1736],809,{},"http://www.agorics.com/",{"_35":204,"_167":1740,"_169":1741,"_41":1743,"_70":1744},[1736],[1742],826,{},"http://www.digicash.com/","\nReferences:\nOliver Williamson, The Economic Institutions of Capitalism\nJanet Landa, Trust, Ethnicity, and Identity\nThe New Palgrave: Allocation, Information, and Markets\nBruce Schneier, Applied Cryptography\nCrypto and Eurocrypt conference proceedings, 1982-1994.\n\"Crypto Rebels\", Wired #2, also cypherpunks mailing list\n(mail to majordomo@toad.com with body \"subscribe cypherpunks\")\nPerry H. Beaumont, Fixed Income Synthetic Assets\nFrederich Hayek, The Fatal Conceit\nMing Li & Paul Vitanyi, An Introduction to Kolmogorov Complexity\nand Its Applications\nVernor Vinge, \"True Names\" (fiction), from True Names and Other Dangers\nMixmaster (ptr to web site)\nPGP (ptr to web site)\nTim May, \"Cyphernomicon\"\nDavid Chaum, \"Security Without Identification\"\nDavid Chaum, \"Achieving Electronic Privacy\"\nAgorics web site\nDigiCash web site",[279],"/records/smart-contracts-building-blocks-for-digital-markets",{"_82":463,"_464":465},{},{"_37":444,"_95":53,"_54":1751,"_71":447,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,446],1772031973273,[149,444,447],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/smart-contracts-building-blocks-for-digital-markets\",\"bafy2bzacedso2tbfaqqnb7vynu5xk4p7icmlkcfpe4htnliggod5tumtjgwpy\"]",{"_110":1756,"_147":3504,"_150":3505},{"_112":1757,"_131":132,"_133":3503,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":1758,"_37":3501},{"_28":1759,"_71":471,"_72":53,"_73":3496,"_54":3497,"_76":480,"_78":3498,"_80":3499,"_84":3500,"_86":481,"_88":89},[1760,1767,1774,1787,1793,1814,1828,1842,1928,2005,3155,3206,3274,3302,3316],{"_31":1761,"_33":1762},[],{"_35":160,"_37":1763,"_39":481,"_41":1764,"_66":1765,"_68":1766,"_70":69},"PJOM2Ch2",{},[],"Working Draft 1.5 20th June 1997",{"_31":1768,"_33":1769},[],{"_35":160,"_37":1770,"_39":481,"_41":1771,"_66":1772,"_68":1773,"_70":69},"YH88J_MV",{},[],"Authors Hugh Davis, Sigi Reich, Antoine Rizk",{"_31":1775,"_33":1776},[],{"_35":160,"_37":1777,"_39":471,"_41":1778,"_66":1779,"_68":1786,"_70":69},"wNACgMRS",{},[1780],{"_35":204,"_167":1781,"_169":1782,"_41":1784,"_70":1785},[240],[1783],55,{},"https://www.southampton.ac.uk/~hcd/ohp/ohp3.htm","Source: https://www.southampton.ac.uk/~hcd/ohp/ohp3.htm",{"_31":1788,"_33":1789},[],{"_35":160,"_37":1790,"_39":471,"_41":1791,"_66":1792,"_68":69,"_70":69},"34Cbndwa",{},[],{"_31":1794,"_33":1809},[1795],{"_31":1796,"_33":1797},[],{"_35":160,"_37":1798,"_39":481,"_41":1799,"_66":1800,"_68":1808,"_70":69},"B5QSopD3",{},[1801],{"_35":204,"_167":1802,"_169":1804,"_41":1806,"_70":1807},[1803],151,[1805],176,{},"mailto:H.C.Davis@ecs.soton.ac.uk","This document specifies the draft for the Open Hypermedia Systems' Protocol (OHP). Distribution of this document is unlimited. Comments are welcome at H.C.Davis@ecs.soton.ac.uk. For discussions about the protocol as well as Open Hypermedia Systems in general see also the OHS Mailing List and the OHS Working Group Home Page.",{"_35":870,"_37":1810,"_39":481,"_41":1811,"_66":1812,"_68":1813,"_70":69},"1Zv9pRDy",{"_273":323},[],"Status of this Document",{"_31":1815,"_33":1823},[1816],{"_31":1817,"_33":1818},[],{"_35":160,"_37":1819,"_39":481,"_41":1820,"_66":1821,"_68":1822,"_70":69},"Zg3ePcux",{},[],"This section should give a management summary and overview. What is the motivation behind OHP? What would be the benefits if OHP would be supported by tools? (viewer independent of linkservice, link editing possible, ...) Should we mention why http is insufficient (because Web users might be interested)?",{"_35":870,"_37":1824,"_39":481,"_41":1825,"_66":1826,"_68":1827,"_70":69},"KkK2fhan",{"_273":323},[],"Abstract",{"_31":1829,"_33":1837},[1830],{"_31":1831,"_33":1832},[],{"_35":160,"_37":1833,"_39":481,"_41":1834,"_66":1835,"_68":1836,"_70":69},"nmdXAZt1",{},[],"This section specifies the actual form and the minimum set of messages defined in OHP. We describe the message header and the messages to be sent; we evolve on specific issues such as location specifications, presentation specifications, and expected functionality and behaviour of components. We finish with example scenarios, related work, and a list of references.",{"_35":870,"_37":1838,"_39":481,"_41":1839,"_66":1840,"_68":1841,"_70":69},"FIKb9Sf9",{"_273":323},[],"Protocol Definition",{"_31":1843,"_33":1922},[1844,1858,1865,1872,1881,1896,1909],{"_31":1845,"_33":1846},[],{"_35":160,"_37":1847,"_39":481,"_41":1848,"_66":1849,"_68":1857,"_70":69},"XO_29Xvj",{},[1850],{"_35":919,"_167":1851,"_169":1853,"_41":1856,"_70":69},[1708,1701,1852],327,[186,1854,1855],230,339,{},"The Open Hypermedia Protocol (OHP) is to be used as a standardised protocol between viewers and link services. These agents of OHP transactions can be of various forms: a Viewer can be a dedicated viewer for a specific LinkService; or it can be an adapted version of an existing generic application such as Microsoft Word. The LinkService can be a 'simple' LinkService providing only links as well as a hyperbase providing both, links and documents. For the remainder of this contribution we will only use the terms Viewer and LinkService for these components.",{"_31":1859,"_33":1860},[],{"_35":160,"_37":1861,"_39":481,"_41":1862,"_66":1863,"_68":1864,"_70":69},"NiKDc_wr",{},[],"In this paper we are concerned with enabling applications to make them link service aware, so that users may have access to the full range of hypermedia functionality from their standard desktop environment. Many of the current generation of hypermedia systems such as DHM (Grønbæk & Trigg, 1992) HyperDisco (Wiil, 1996), Microcosm (Davis et al., 1994), Multicard (Rizk & Sauter, 1992) and the Texas A&M system prototypes (e.g. Kacmar & Leggett, 1991) have addressed this problem, but so far no standard has emerged due to the different hypertext data models and communication protocols adopted by these systems.",{"_31":1866,"_33":1867},[],{"_35":160,"_37":1868,"_39":481,"_41":1869,"_66":1870,"_68":1871,"_70":69},"9R4-aDDa",{},[],"For the definition of the protocol we additionally make some assumptions on the architecture. Note however, that we are not aiming and not claiming for fully defining a reference architecture. The general picture we have in mind when defining OHP is as follows:",{"_31":1873,"_33":1874},[],{"_35":1875,"_37":1876,"_39":481,"_41":1877,"_66":1878,"_68":1879,"_70":1880},"Image","Xlbh4XN8",{"_273":323},[],"Fig.: Components and Layers in OHP Definition","ipfs://bafkreih7jzzwm3ki5astug5rimimh6jy37izxadjh7gaxxsnnvktchs7di",{"_31":1882,"_33":1883},[],{"_35":160,"_37":1884,"_39":481,"_41":1885,"_66":1886,"_68":1895,"_70":69},"q6Xdmi3F",{},[1887],{"_35":919,"_167":1888,"_169":1891,"_41":1894,"_70":69},[1117,1889,1890],274,291,[1892,954,1893],87,300,{},"In defining OHP we abstracted in different layers. On the top-level a so-called Viewer talks OHP to another component which is only interesting from an OHP point of view in that this component understands and answers OHP requests. Typically though this component would be a LinkService or a HyperBase.",{"_31":1897,"_33":1898},[],{"_35":160,"_37":1899,"_39":481,"_41":1900,"_66":1901,"_68":1908,"_70":69},"7U9dsRnk",{},[1902],{"_35":919,"_167":1903,"_169":1905,"_41":1907,"_70":69},[1904],206,[1906],221,{},"OHP abstracts from the communication layer. However, there has to be a component that establishes connections, that 'knows' how to talk to other services and viewers, and the more. We call this component a SessionManager and it could be described as an intermediate component between LinkService and Viewer. For the definition of OHP we assume that both Viewer and LinkService exchange OHP messages via the SessionManager, the actual communication though is not part of OHP.",{"_31":1910,"_33":1911},[],{"_35":160,"_37":1912,"_39":481,"_41":1913,"_66":1914,"_68":1921,"_70":69},"0ytvTdvJ",{},[1915],{"_35":919,"_167":1916,"_169":1918,"_41":1920,"_70":69},[921,1917],443,[1919,1703],122,{},"Besides the components Viewer, LinkService and SessionManager there is a fourth component, the Document Management System (DMS). We are convinced that an additional protocol - a document management procotocol (DMP) - should allow standardised communication to document management systems. The Open Document Management API (Open Document Management, 1997) could serve as a good example and some of the concepts in OHP, e.g. the definition of a NodeId as a unique document identifier, follow this proposal.",{"_35":870,"_37":1923,"_39":1924,"_41":1925,"_66":1926,"_68":1927,"_70":69},"W35eityG","bafy2bzaceaimazzdifw7xyhsjnce5bwn2a2lxrvhipfyrlgsx5wmgjba25owu",{"_273":323},[],"4. Introduction",{"_31":1929,"_33":2000},[1930,1944],{"_31":1931,"_33":1939},[1932],{"_31":1933,"_33":1934},[],{"_35":160,"_37":1935,"_39":481,"_41":1936,"_66":1937,"_68":1938,"_70":69},"KJCwLCuI",{},[],"OHP is a peer to peer asynchronous protocol. Messages may be sent by either the LinkService or by the Viewer. If a reply is expected, it is up to the receiving component to initiate a new message. There are thus two main classes of messages to be considered; those sent by the Viewer and those sent by the LinkService.",{"_35":870,"_37":1940,"_39":481,"_41":1941,"_66":1942,"_68":1943,"_70":69},"uZuoKZII",{"_273":323},[],"5.1 General Form",{"_31":1945,"_33":1995},[1946,1953,1960,1967,1974,1981,1988],{"_31":1947,"_33":1948},[],{"_35":160,"_37":1949,"_39":481,"_41":1950,"_66":1951,"_68":1952,"_70":69},"GOwHSYvv",{},[],"For actually defining the mechanics of OHP we will follow a Backus-Naur Form (BNF) as is for instance done in Internet drafts. We use the following constructs:",{"_31":1954,"_33":1955},[],{"_35":160,"_37":1956,"_39":481,"_41":1957,"_66":1958,"_68":1959,"_70":69},"yGjm52Mj",{},[],"name = definition: The name of a rule is simply the name itself and is separated from its definition by the equal \"=\" character.\n\"literal\": defines a literal. Definition is case sensitive.\n{elem1 | elem2}: a \"|\" can be used to define either/or alternatives.",{"_31":1961,"_33":1962},[],{"_35":160,"_37":1963,"_39":481,"_41":1964,"_66":1965,"_68":1966,"_70":69},"6Jfl-S5P",{},[],"{elem}*: A \"*\" indicates repetition, i.e. there can be any number of occurrences.\n{elem}+: A \"+\" indicates that one or more elements have to be present, i.e. there has to be at least one element.\n[elem]: Square brackets enclose optional elements.\n: Angle brackets enclose basic types that are not specified in more detail but can be dealt with by the receiving/sending components.",{"_31":1968,"_33":1969},[],{"_35":160,"_37":1970,"_39":481,"_41":1971,"_66":1972,"_68":1973,"_70":69},"ie1Lvb-h",{},[],"Additionally we assume the following rules (the US-ASCII coded character set is defined by ANSI X3.4- 1986):",{"_31":1975,"_33":1976},[],{"_35":160,"_37":1977,"_39":481,"_41":1978,"_66":1979,"_68":1980,"_70":69},"hercYcQY",{},[],"CHAR = US-ASCII character (octets 0 - 127)\nUPALPHA = any US-ASCII uppercase letter \"A\"..\"Z\"\nLOALPHA = any US-ASCII lowercase letter \"a\"..\"z\"\nALPHA = UPALPHA | LOALPHA\nDIGIT = any US-ASCII digit \"0\"..\"9\"\nCTL = any US-ASCII control character (octets 0 - 31) and DEL (127) CR = US-ASCII CR, carriage return (13)\nLF = US-ASCII LF, linefeed (10)\nSP = US-ASCII SP, space (32)",{"_31":1982,"_33":1983},[],{"_35":160,"_37":1984,"_39":481,"_41":1985,"_66":1986,"_68":1987,"_70":69},"qo5akUzo",{},[],"OHP messages will consist of text strings (CHAR). In the following sections the messages are shown formatted on multiple lines for ease of presentation. However, the messages themselves will be one continuous stream of ASCII text, unbroken by line feeds (LF). The messages consist of Tags, which are proceeded by a backslash ('\\') and succeeded by a white space (SP). The characters that follow, up to the next tag or the end of the message are the tag contents. A tag content may be empty if shown as optional in the message definition. The tags of each message are all compulsory, and must be presented in the order of the message definition. If a backslash ('\\') occurs within the tag content, then it should be quoted by preceding it with a further backslash.",{"_31":1989,"_33":1990},[],{"_35":160,"_37":1991,"_39":481,"_41":1992,"_66":1993,"_68":1994,"_70":69},"M83RmpNI",{},[],"We can now begin to define the protocol.",{"_35":870,"_37":1996,"_39":481,"_41":1997,"_66":1998,"_68":1999,"_70":69},"zbuQ8w_-",{"_273":323},[],"5.2 Notational Conventions and Generic Grammar",{"_35":870,"_37":2001,"_39":481,"_41":2002,"_66":2003,"_68":2004,"_70":69},"DY3XRv8Z",{"_273":323},[],"5. Form of the Protocol",{"_31":2006,"_33":3150},[2007,2078,2128,2836,3067],{"_31":2008,"_33":2073},[2009,2016,2023,2032,2039,2046,2053,2060],{"_31":2010,"_33":2011},[],{"_35":160,"_37":2012,"_39":481,"_41":2013,"_66":2014,"_68":2015,"_70":69},"__YPR-8R",{},[],"As opposed to the previous draft of OHP (Davis et al., 1996), which define a Channel as an identifier for messages, we have defined a dedicated message header (see Thread \"Channels in OHP\"). As already mentioned above, OHP abstracts from the communication layer so the header does not include any host or port or other communication specific information.",{"_31":2017,"_33":2018},[],{"_35":160,"_37":2019,"_39":481,"_41":2020,"_66":2021,"_68":2022,"_70":69},"2ObolEcf",{},[],"The OHP message header is defined as",{"_31":2024,"_33":2025},[],{"_35":2026,"_37":2027,"_39":481,"_41":2028,"_66":2030,"_68":2031,"_70":69},"Code","iglg_-0L",{"_2029":69},"language",[],"MessHeader = \\MessId the OHP Id and version number\n \\Subject name of this message\n",{"_31":2033,"_33":2034},[],{"_35":160,"_37":2035,"_39":481,"_41":2036,"_66":2037,"_68":2038,"_70":69},"c4l8SJPU",{},[],"MessId uniquely identifies this type of message and gives OHP version information. The subject field is considered to be particularely helpful in case a component can not understand a message; it could then at least provide additional information about the message.",{"_31":2040,"_33":2041},[],{"_35":160,"_37":2042,"_39":481,"_41":2043,"_66":2044,"_68":2045,"_70":69},"Bkp_I0A-",{},[],"Besides basic header information there are two more fields that will be present in almost all messages but that do not have to be understood by the LinkService. These fields are",{"_31":2047,"_33":2048},[],{"_35":2026,"_37":2049,"_39":481,"_41":2050,"_66":2051,"_68":2052,"_70":69},"DmouUDKL",{"_2029":69},[],"\\SessionId a byte string that can be used for uniquely identifying\n messages and deal with transaction management\n",{"_31":2054,"_33":2055},[],{"_35":2026,"_37":2056,"_39":481,"_41":2057,"_66":2058,"_68":2059,"_70":69},"2brspFC6",{"_2029":69},[],"\\UserId a byte string that can be used for identifying a user\n",{"_31":2061,"_33":2062},[],{"_35":160,"_37":2063,"_39":481,"_41":2064,"_66":2065,"_68":2072,"_70":69},"Y4DPyli5",{},[2066],{"_35":919,"_167":2067,"_169":2069,"_41":2071,"_70":69},[2068],167,[2070],173,{},"As mentioned above, the actual managing of documents is a crucial issue. Within OHP, documents are therfore not dealt with directly but are called by a reference, the NodeId. A NodeId has to be unique within a given usage scenario. However, from a protocol perspective the NodeId is opaque.",{"_35":870,"_37":2074,"_39":481,"_41":2075,"_66":2076,"_68":2077,"_70":69},"aNUXkyG0",{"_273":323},[],"6.1 Message Header",{"_31":2079,"_33":2123},[2080,2087,2116],{"_31":2081,"_33":2082},[],{"_35":160,"_37":2083,"_39":481,"_41":2084,"_66":2085,"_68":2086,"_70":69},"jqMeAPR6",{},[],"The abstraction from communication information within the OHP header requires a number of assumptions about the underlying components' functionality. The main component both LinkService and Viewer will be talking to is the so-called \"SessionManager\". Note that there is a manifold of different terms for this component: in the previous draft of OHP it has been called \"Communication Protocol Shim\" (Davis et al., 1996), (Goose et al., 1997) call it \"Runtime\", (Wiil and Leggett, 1996) call it \"Tool integrator\"; all approaches have in common that they require a component at the client's side managing different OHP sessions. That's why we use the term SessionManager.",{"_31":2088,"_33":2110},[2089,2096,2103],{"_31":2090,"_33":2091},[],{"_35":160,"_37":2092,"_39":481,"_41":2093,"_66":2094,"_68":2095,"_70":69},"HOv08E0l",{},[],"Establishing of connections to the LinkServices the user wants to connect; transfering and receiving of OHP messages;",{"_31":2097,"_33":2098},[],{"_35":160,"_37":2099,"_39":481,"_41":2100,"_66":2101,"_68":2102,"_70":69},"C_ZpoFlz",{},[],"Loading of documents if asked to by the LaunchDocument message; the parameter given is of type NodeId.",{"_31":2104,"_33":2105},[],{"_35":160,"_37":2106,"_39":481,"_41":2107,"_66":2108,"_68":2109,"_70":69},"E90Z2CNE",{},[],"Providing of document management functions in the absence of a document management system. The SessionManager should then do tasks such as providing attribute access functions for a given document (its NickName, Type, Preferred Viewer etc.). ",{"_35":160,"_37":2111,"_39":481,"_41":2112,"_66":2114,"_68":2115,"_70":69},"XY8HXIvO",{"_273":2113},"Ordered",[],"This is the basic functionality and behaviour we are assuming a SessionManager component to have:",{"_31":2117,"_33":2118},[],{"_35":160,"_37":2119,"_39":481,"_41":2120,"_66":2121,"_68":2122,"_70":69},"oDedjJ4O",{},[],"Additionally, as creation of links between node in different application windows is a crucial issue, also this functionality could be part of the SessionManager. Issues such as joining n to m anchors, defining direction, scope etc. would probably be best implemented just once in the Session Manager. This means that the SessionManager not in some implementations might not only be a process but also have a user interface component available to all applications on a user's desktop.",{"_35":870,"_37":2124,"_39":481,"_41":2125,"_66":2126,"_68":2127,"_70":69},"ZYLUIKY6",{"_273":323},[],"6.2 Responsibilities of Session Manager",{"_31":2129,"_33":2831},[2130,2140,2189,2238,2245,2252,2264,2271,2283,2290,2297,2304,2332,2339,2346,2358,2365,2372,2379,2386,2393,2400,2407,2419,2440,2447,2454,2461,2468,2480,2487,2494,2501,2508,2515,2522,2534,2541,2548,2559,2566,2573,2584,2591,2598,2609,2616,2623,2630,2637,2644,2651,2663,2670,2677,2688,2695,2702,2748,2773,2798,2805],{"_31":2131,"_33":2132},[],{"_35":1875,"_37":2133,"_39":481,"_41":2134,"_66":2137,"_68":2138,"_70":2139},"DftirzAK",{"_273":323,"_2135":2136},"width",601.4423076923077,[],"Tab.: Message Requests by Viewer and Answers by LinkService","ipfs://bafkreihvczqllcwg35r3oo4etug32fhrwfjoha35533sb2fbnapq6ar5xi",{"_31":2141,"_33":2184},[2142,2149,2156,2163,2170,2177],{"_31":2143,"_33":2144},[],{"_35":160,"_37":2145,"_39":481,"_41":2146,"_66":2147,"_68":2148,"_70":69},"Al-TzK2M",{},[],"RequestService",{"_31":2150,"_33":2151},[],{"_35":160,"_37":2152,"_39":481,"_41":2153,"_66":2154,"_68":2155,"_70":69},"E9QU1_-3",{},[],"ClosingNode",{"_31":2157,"_33":2158},[],{"_35":160,"_37":2159,"_39":481,"_41":2160,"_66":2161,"_68":2162,"_70":69},"n0DlHdEP",{},[],"UpdateAnchors",{"_31":2164,"_33":2165},[],{"_35":160,"_37":2166,"_39":481,"_41":2167,"_66":2168,"_68":2169,"_70":69},"ldBjJKeX",{},[],"UpdateNode",{"_31":2171,"_33":2172},[],{"_35":160,"_37":2173,"_39":481,"_41":2174,"_66":2175,"_68":2176,"_70":69},"wXkiaOPX",{},[],"CreateLink",{"_31":2178,"_33":2179},[],{"_35":160,"_37":2180,"_39":481,"_41":2181,"_66":2182,"_68":2183,"_70":69},"VzRLCAfI",{},[],"CreateNode",{"_35":160,"_37":2185,"_39":481,"_41":2186,"_66":2187,"_68":2188,"_70":69},"dCFNG3Tp",{"_273":274},[],"Additionally, the Viewer might send the following messages:",{"_31":2190,"_33":2233},[2191,2198,2205,2212,2219,2226],{"_31":2192,"_33":2193},[],{"_35":160,"_37":2194,"_39":481,"_41":2195,"_66":2196,"_68":2197,"_70":69},"-z0P6KgH",{},[],"LaunchDocument",{"_31":2199,"_33":2200},[],{"_35":160,"_37":2201,"_39":481,"_41":2202,"_66":2203,"_68":2204,"_70":69},"eLpwq2AW",{},[],"DisplayAnchor",{"_31":2206,"_33":2207},[],{"_35":160,"_37":2208,"_39":481,"_41":2209,"_66":2210,"_68":2211,"_70":69},"mlHoF69B",{},[],"DisplayLocSpec",{"_31":2213,"_33":2214},[],{"_35":160,"_37":2215,"_39":481,"_41":2216,"_66":2217,"_68":2218,"_70":69},"_YVP2R3G",{},[],"Interpret",{"_31":2220,"_33":2221},[],{"_35":160,"_37":2222,"_39":481,"_41":2223,"_66":2224,"_68":2225,"_70":69},"Qz0G3GqF",{},[],"NewAnchor",{"_31":2227,"_33":2228},[],{"_35":160,"_37":2229,"_39":481,"_41":2230,"_66":2231,"_68":2232,"_70":69},"dyQJFmG5",{},[],"CloseNode",{"_35":160,"_37":2234,"_39":481,"_41":2235,"_66":2236,"_68":2237,"_70":69},"eD-4lQHT",{"_273":274},[],"The LinkService might send the following messages to the Viewer",{"_31":2239,"_33":2240},[],{"_35":160,"_37":2241,"_39":481,"_41":2242,"_66":2243,"_68":2244,"_70":69},"LHz2UZEa",{},[],"All, Viewer, LinkService as well as other components speaking OHP can send an error message.",{"_31":2246,"_33":2247},[],{"_35":160,"_37":2248,"_39":481,"_41":2249,"_66":2250,"_68":2251,"_70":69},"MSNBn7dD",{},[],"We will now present the messages in detail and also give examples or additional comments where necessary to understand the semantics of the protocol.",{"_31":2253,"_33":2254},[],{"_35":160,"_37":2255,"_39":481,"_41":2256,"_66":2257,"_68":2263,"_70":69},"9txblX-L",{},[2258],{"_35":166,"_167":2259,"_169":2260,"_41":2262,"_70":69},[137],[2261],35,{},"Message Pair \"GetServices/Services\"",{"_31":2265,"_33":2266},[],{"_35":160,"_37":2267,"_39":481,"_41":2268,"_66":2269,"_68":2270,"_70":69},"Xbw6TqEq",{},[],"The \"GetServices\" message is to be sent from Viewer to LinkService in order to know which services are available. The LinkService has to answer this request by a \"Services\" message. Services are defined by a description and a service name.",{"_31":2272,"_33":2273},[],{"_35":160,"_37":2274,"_39":481,"_41":2275,"_66":2276,"_68":2282,"_70":69},"HexKkp0u",{},[2277],{"_35":919,"_167":2278,"_169":2279,"_41":2281,"_70":69},[137],[2280],402,{},"Note the naming of message IDs in OHP: \"MV\" is short for \"message from viewer\", the second token gives the name of the message and the last two tokens define that the message class this message belongs to is OHP and give version information. Equally, service originated messages start with \"MS\", short for \"message from service\". Messages that can be originated by any of the components start with \"M\".",{"_31":2284,"_33":2285},[],{"_35":2026,"_37":2286,"_39":481,"_41":2287,"_66":2288,"_68":2289,"_70":69},"63Nft9kV",{"_2029":69},[],"\\MessId MV_GetServices_OHP_1.0\n\\Subject \"GetServices\"\n\\SessionId \n\\UserId \n",{"_31":2291,"_33":2292},[],{"_35":160,"_37":2293,"_39":481,"_41":2294,"_66":2295,"_68":2296,"_70":69},"s1Ej0tAZ",{},[],"The linkservice will reply with",{"_31":2298,"_33":2299},[],{"_35":2026,"_37":2300,"_39":481,"_41":2301,"_66":2302,"_68":2303,"_70":69},"jtQrzjLo",{"_2029":69},[],"\n\\MessId MS_Services_OHP_1.0\n\\Subject \"Services\"\n\\Data\n {\\Service the name of the service\n \\Description a description of the service in the\n local language}+\n\\SessionId \n\\UserId \n",{"_31":2305,"_33":2327},[2306,2313,2320],{"_31":2307,"_33":2308},[],{"_35":160,"_37":2309,"_39":481,"_41":2310,"_66":2311,"_68":2312,"_70":69},"nOTxxuJs",{},[],"FollowLink",{"_31":2314,"_33":2315},[],{"_35":160,"_37":2316,"_39":481,"_41":2317,"_66":2318,"_68":2319,"_70":69},"VIwN4S3i",{},[],"MakeAnchor - which must also add the service for the anchor ",{"_31":2321,"_33":2322},[],{"_35":160,"_37":2323,"_39":481,"_41":2324,"_66":2325,"_68":2326,"_70":69},"zm6FNx7t",{},[],"DeleteAnchor",{"_35":160,"_37":2328,"_39":481,"_41":2329,"_66":2330,"_68":2331,"_70":69},"pcJPub5S",{"_273":274},[],"We have identified a number of default services that each LinkService supporting OHP has to provide. These services include",{"_31":2333,"_33":2334},[],{"_35":160,"_37":2335,"_39":481,"_41":2336,"_66":2337,"_68":2338,"_70":69},"6S1rBcJd",{},[],"Any of these services may be requested by a \"RequestService\" message, for instance",{"_31":2340,"_33":2341},[],{"_35":2026,"_37":2342,"_39":481,"_41":2343,"_66":2344,"_68":2345,"_70":69},"N5yypQGE",{"_2029":69},[],"\\MessId MS_RequestService_OHP_1.0\n\\Subject \"RequestService\"\n\\Service \"FollowLink\"\n\\AnchorId 152.78.115.213:D:999\n\\LocSpec {\\ContentType ASCII\n \\Content \"OHS Home Page\" \\LocType \"NameLoc\"\n \\NodeId 152.78.115.213:E:3334}\n\\Presentation\n\\SessionId 33\n\\UserId Hugh\n",{"_31":2347,"_33":2348},[],{"_35":160,"_37":2349,"_39":481,"_41":2350,"_66":2351,"_68":2357,"_70":69},"YcsEWwgd",{},[2352],{"_35":166,"_167":2353,"_169":2354,"_41":2356,"_70":69},[137],[2355],31,{},"Message Pair \"GetNodeId/NodeId\"",{"_31":2359,"_33":2360},[],{"_35":160,"_37":2361,"_39":481,"_41":2362,"_66":2363,"_68":2364,"_70":69},"RaD49SwR",{},[],"OHP does not actually deal with the documents being involved in an OHP session; it uses references to documents instead. However, in many situations it might be useful to get a document identifier given the name of a document or any of its attributed. For this purpose the message pair \"GetNodeId / NodeId\" is introduced.",{"_31":2366,"_33":2367},[],{"_35":2026,"_37":2368,"_39":481,"_41":2369,"_66":2370,"_68":2371,"_70":69},"y-EAdz7E",{"_2029":69},[],"\\MessId MV_GetNodeId_OHP_1.0\n\\Subject \"GetNodeId\"\n\\DocumentName the name of the document\n\\DocumentAttributes\n {\\name the attribute's name\n \\value its value}*\n\\SessionId \n\\UserId ",{"_31":2373,"_33":2374},[],{"_35":160,"_37":2375,"_39":481,"_41":2376,"_66":2377,"_68":2378,"_70":69},"Sdz8IrKr",{},[],"The LinkServer will answer this request with",{"_31":2380,"_33":2381},[],{"_35":2026,"_37":2382,"_39":481,"_41":2383,"_66":2384,"_68":2385,"_70":69},"ayCTb1Xk",{"_2029":69},[],"\\MessId MS_NodeId_OHP_1.0\n\\Subject \"NodeId\"\n[\\NodeId NodeId | \\result a result message string]\n\\SessionId \n\\UserId \n",{"_31":2387,"_33":2388},[],{"_35":160,"_37":2389,"_39":481,"_41":2390,"_66":2391,"_68":2392,"_70":69},"QivueXer",{},[],"If there is no NodeId for the given document name and attributes then the document is either currently unknown to the LinkService or it is unavailable (it could for instance be locked). The LinkService specifies this in the result tag. It is the responsibility of the SessionManager to register this node or pass the error on to the user. In case it wants to reister a new node the SessionManager would send",{"_31":2394,"_33":2395},[],{"_35":2026,"_37":2396,"_39":481,"_41":2397,"_66":2398,"_68":2399,"_70":69},"qxJNuXlT",{"_2029":69},[],"\\MessId MV_CreateNode_OHP_1.0\n\\Subject \"CreateNode\"\n\\DocumentName the name of the document\n\\DocumentAttributes\n {\\name the attribute's name\n \\value its value}*\n\\SessionId \n\\UserId ",{"_31":2401,"_33":2402},[],{"_35":160,"_37":2403,"_39":481,"_41":2404,"_66":2405,"_68":2406,"_70":69},"RyIoZRqp",{},[],"The LinkServer will eventually send back a NodeId message (see above).",{"_31":2408,"_33":2409},[],{"_35":160,"_37":2410,"_39":481,"_41":2411,"_66":2412,"_68":2418,"_70":69},"qsJ-Qlx1",{},[2413],{"_35":166,"_167":2414,"_169":2415,"_41":2417,"_70":69},[137],[2416],41,{},"Message Pair \"GetAnchorTable/AnchorTable\"",{"_31":2420,"_33":2435},[2421,2428],{"_31":2422,"_33":2423},[],{"_35":160,"_37":2424,"_39":481,"_41":2425,"_66":2426,"_68":2427,"_70":69},"eAY-GLd-",{},[],"a. What services it may offer (see above)",{"_31":2429,"_33":2430},[],{"_35":160,"_37":2431,"_39":481,"_41":2432,"_66":2433,"_68":2434,"_70":69},"Dmw5uy_C",{},[],"b. What anchors to display in the current document",{"_35":160,"_37":2436,"_39":481,"_41":2437,"_66":2438,"_68":2439,"_70":69},"q8IwcNsY",{"_273":323},[],"Now that we have the document itself and an appropriate application for the document, the application needs to know",{"_31":2441,"_33":2442},[],{"_35":160,"_37":2443,"_39":481,"_41":2444,"_66":2445,"_68":2446,"_70":69},"LmL7OKPO",{},[],"In order to get the anchors for a given document (represented by its NodeId) the GetAnchorTable message is used. Note that the message is asynchronous, and that it should result in one or more AnchorTable messages, e.g. if a distributed LinkService came up with separate answers. The application should be capable of concatenating the tables.",{"_31":2448,"_33":2449},[],{"_35":2026,"_37":2450,"_39":481,"_41":2451,"_66":2452,"_68":2453,"_70":69},"yD-J0LWG",{"_2029":69},[],"\\MessId MV_GetAnchorTable_OHP_1.0\n\\Subject \"GetAnchorTable\"\n\\NodeId \n\\SessionId \n\\UserId \n",{"_31":2455,"_33":2456},[],{"_35":160,"_37":2457,"_39":481,"_41":2458,"_66":2459,"_68":2460,"_70":69},"NZWdjssj",{},[],"The LinkService should answer this with the \"AnchorTable\" message.",{"_31":2462,"_33":2463},[],{"_35":2026,"_37":2464,"_39":481,"_41":2465,"_66":2466,"_68":2467,"_70":69},"-dA-TEJb",{"_2029":69},[],"\\MessId MS_AnchorTable_OHP_1.0\n\\Subject \"AnchorTable\"\n\\NodeId \n\\Data {\\AnchorId \\LocSpec\n \\Direction {\"AtoB\" | \"bidirectional\"} \\Presentation \\Service}+\n\\SessionId \n\\UserId \n",{"_31":2469,"_33":2470},[],{"_35":160,"_37":2471,"_39":481,"_41":2472,"_66":2473,"_68":2479,"_70":69},"FkmJcE3U",{},[2474],{"_35":166,"_167":2475,"_169":2476,"_41":2478,"_70":69},[137],[2477],34,{},"Message Pair \"CreateLinkId/LinkId\"",{"_31":2481,"_33":2482},[],{"_35":160,"_37":2483,"_39":481,"_41":2484,"_66":2485,"_68":2486,"_70":69},"p3qSDiLF",{},[],"This message is sent by the Viewer - it could also be sent by the SessionManager's user interface component - when a user creates a link. OHP allows any number of incoming and outging anchor ids; a link at least has a direction and a name. The CreateLinkId message should be answered by the LinkService with a LinkId message (see below). If the creation of the link has not been successful for any reason a result tag instead of a LinkId should be answered.",{"_31":2488,"_33":2489},[],{"_35":2026,"_37":2490,"_39":481,"_41":2491,"_66":2492,"_68":2493,"_70":69},"J7LgI-Q-",{"_2029":69},[],"\\MessId MV_CreateLinkId_OHP_1.0\n\\Subject \"CreateLinkId\"\n\\AAnchors {\\AnchorId }+\n\\BAnchors {\\AnchorId }+\n\\Direction {\"AtoB\" | \"bidirectional\"}\n\\Description textual description of the link\n\\SessionId \n\\UserId \n",{"_31":2495,"_33":2496},[],{"_35":160,"_37":2497,"_39":481,"_41":2498,"_66":2499,"_68":2500,"_70":69},"JPoQclE-",{},[],"The LinkServer's answer",{"_31":2502,"_33":2503},[],{"_35":2026,"_37":2504,"_39":481,"_41":2505,"_66":2506,"_68":2507,"_70":69},"bq0jU9gU",{"_2029":69},[],"\\MessId MS_LinkId_OHP_1.0\n\\Subject \"LinkId\"\n[\\LinkId LinkId | \\result a result message string]\n\\SessionId \n\\UserId \n",{"_31":2509,"_33":2510},[],{"_35":160,"_37":2511,"_39":481,"_41":2512,"_66":2513,"_68":2514,"_70":69},"200yI5Xg",{},[],"Delete as well as update link messages are omitted as those are supposed to be done at the LinkService. It",{"_31":2516,"_33":2517},[],{"_35":160,"_37":2518,"_39":481,"_41":2519,"_66":2520,"_68":2521,"_70":69},"ojfgEuk0",{},[],"is not clear that there is a simple interface to this function which could be provided at the client end.",{"_31":2523,"_33":2524},[],{"_35":160,"_37":2525,"_39":481,"_41":2526,"_66":2527,"_68":2533,"_70":69},"8GpLRnDJ",{},[2528],{"_35":166,"_167":2529,"_169":2530,"_41":2532,"_70":69},[137],[2531],24,{},"Message \"RequestService\"",{"_31":2535,"_33":2536},[],{"_35":160,"_37":2537,"_39":481,"_41":2538,"_66":2539,"_68":2540,"_70":69},"Tk5flQtm",{},[],"The RequestService message is a very general message that can be used by the Viewer to request a LinkService to do one of its services. The available services can be retrieved by the GetServices message.",{"_31":2542,"_33":2543},[],{"_35":2026,"_37":2544,"_39":481,"_41":2545,"_66":2546,"_68":2547,"_70":69},"3UXb5HBQ",{"_2029":69},[],"\\MessId MV_RequestService_OHP_1.0\n\\Subject \"RequestService\"\n\\Service name of the service\n\\AnchorId \n\\LocSpec\n\\Presentation\n\\SessionId \n\\UserId ",{"_31":2549,"_33":2550},[],{"_35":160,"_37":2551,"_39":481,"_41":2552,"_66":2553,"_68":2558,"_70":69},"JUztBI8m",{},[2554],{"_35":166,"_167":2555,"_169":2556,"_41":2557,"_70":69},[137],[1556],{},"Message \"ClosingNode\"",{"_31":2560,"_33":2561},[],{"_35":160,"_37":2562,"_39":481,"_41":2563,"_66":2564,"_68":2565,"_70":69},"vYIMAbb1",{},[],"This message is sent from the Viewer to the LinkService when a node is closed by the user.",{"_31":2567,"_33":2568},[],{"_35":2026,"_37":2569,"_39":481,"_41":2570,"_66":2571,"_68":2572,"_70":69},"3lTKQZIS",{"_2029":69},[],"\\MessId MV_ClosingNode_OHP_1.0\n\\Subject \"ClosingNode\"\n\\NodeId \n\\SessionId \n\\UserId \n",{"_31":2574,"_33":2575},[],{"_35":160,"_37":2576,"_39":481,"_41":2577,"_66":2578,"_68":2583,"_70":69},"vUIAMENr",{},[2579],{"_35":166,"_167":2580,"_169":2581,"_41":2582,"_70":69},[137],[2531],{},"Message \"Update Anchors\"",{"_31":2585,"_33":2586},[],{"_35":160,"_37":2587,"_39":481,"_41":2588,"_66":2589,"_68":2590,"_70":69},"F7icghs2",{},[],"The UpdateAnchors message is sent by the Viewer to the LinkService when the Viewer wants to update the existing anchor list for a given NodeId.",{"_31":2592,"_33":2593},[],{"_35":2026,"_37":2594,"_39":481,"_41":2595,"_66":2596,"_68":2597,"_70":69},"4URLio5a",{"_2029":69},[],"\\MessId MV_UpdateAnchors_OHP_1.0\n\\Subject \"UpdateAnchors\"\n\\NodeId \n\\Data {\\AnchorID \\LocSpec \n \\Presentation \\Service }+\n\\SessionId \n\\UserId ",{"_31":2599,"_33":2600},[],{"_35":160,"_37":2601,"_39":481,"_41":2602,"_66":2603,"_68":2608,"_70":69},"GS5e6ypQ",{},[2604],{"_35":166,"_167":2605,"_169":2606,"_41":2607,"_70":69},[137],[2531],{},"Message \"LaunchDocument\"",{"_31":2610,"_33":2611},[],{"_35":160,"_37":2612,"_39":481,"_41":2613,"_66":2614,"_68":2615,"_70":69},"yL77uBsN",{},[],"We start the list of messages being sent by the LinkService to the Viewer with the LaunchDocument message. The LinkService might send this message for instance as the result of a follow link from another application.",{"_31":2617,"_33":2618},[],{"_35":2026,"_37":2619,"_39":481,"_41":2620,"_66":2621,"_68":2622,"_70":69},"X2EgdhUK",{"_2029":69},[],"\\MessId MS_LaunchDocument_OHP_1.0\n\\Subject \"LaunchDocument\"\n\\NodeId \n\\DMS \"SessionManager\" | \"LinkService\"| DMS handle ???\n\\ReadOnly \"True\" | \"False\"\n\\SessionId \n\\UserId ",{"_31":2624,"_33":2625},[],{"_35":160,"_37":2626,"_39":481,"_41":2627,"_66":2628,"_68":2629,"_70":69},"R7lqy57q",{},[],"I think NodeId should be interpreted by the SessionManager. We should not have to deal with the DMS stuff here. LaunchDocument will not have DatacallBack. Instead it will have a DMS field which will have the value \"SessionManager\", \"LinkService\" or the name of the DMS which can interpret the DocId.",{"_31":2631,"_33":2632},[],{"_35":160,"_37":2633,"_39":481,"_41":2634,"_66":2635,"_68":2636,"_70":69},"qR2yjCiV",{},[],"The Viewer might now get the document and - in case in can not deal with the type of document on its own - launch the appropriate Viewer. This will be initiated by advising the SessionManager to to this task.",{"_31":2638,"_33":2639},[],{"_35":160,"_37":2640,"_39":481,"_41":2641,"_66":2642,"_68":2643,"_70":69},"sHGDlp7w",{},[],"The SessionManager may use a document management protocol (DMP) to get the document, or it may do it itself, or ask the LinkService. It may also use DMP to obtain any document attributes, such as nickname, document type and preferred Viewer. If it doesn't do this, then it will be necessary for the SessionManager to supply these values.",{"_31":2645,"_33":2646},[],{"_35":160,"_37":2647,"_39":481,"_41":2648,"_66":2649,"_68":2650,"_70":69},"yjmYu9OP",{},[],"Alternatively, we may have loaded a document and wish to start Link services. ",{"_31":2652,"_33":2653},[],{"_35":160,"_37":2654,"_39":481,"_41":2655,"_66":2656,"_68":2662,"_70":69},"6WwecxJA",{},[2657],{"_35":166,"_167":2658,"_169":2659,"_41":2661,"_70":69},[137],[2660],23,{},"Message \"DisplayAnchor\"",{"_31":2664,"_33":2665},[],{"_35":160,"_37":2666,"_39":481,"_41":2667,"_66":2668,"_68":2669,"_70":69},"wLq8u_yI",{},[],"The LinkService might request from the Viewer to display an anchor in case a document has changed. For this purpose the \"DisplayAnchor\" message is used.",{"_31":2671,"_33":2672},[],{"_35":2026,"_37":2673,"_39":481,"_41":2674,"_66":2675,"_68":2676,"_70":69},"fD_XltQC",{"_2029":69},[],"\n\\MessId MS_DisplayAnchor_OHP_1.0\n\\Subject \"DisplayAnchor\"\n\\SessionId \n\\Subject DisplayAnchor\n\\AnchorID \\Presentation\n\\UserId \n",{"_31":2678,"_33":2679},[],{"_35":160,"_37":2680,"_39":481,"_41":2681,"_66":2682,"_68":2687,"_70":69},"FPxVH53u",{},[2683],{"_35":166,"_167":2684,"_169":2685,"_41":2686,"_70":69},[137],[2531],{},"Message \"DisplayLocSpec\"",{"_31":2689,"_33":2690},[],{"_35":160,"_37":2691,"_39":481,"_41":2692,"_66":2693,"_68":2694,"_70":69},"typ-7dKE",{},[],"Equally, location specifications might wanted to be displayed by the server. ",{"_31":2696,"_33":2697},[],{"_35":2026,"_37":2698,"_39":481,"_41":2699,"_66":2700,"_68":2701,"_70":69},"sYKiTMZd",{"_2029":69},[],"\n\\MessId MS_DisplayLocSpec_OHP_1.0\n\\Subject \"DisplayLocSpec\"\n\\LocSpec \\Presentation\n\\SessionId \n",{"_31":2703,"_33":2739},[2704,2725,2732],{"_31":2705,"_33":2720},[2706,2713],{"_31":2707,"_33":2708},[],{"_35":160,"_37":2709,"_39":481,"_41":2710,"_66":2711,"_68":2712,"_70":69},"sP5yvsGr",{},[],"Server End Scripts. These are the scripts that are carried out when some particular event occurs or some action is requested. From the point of view of the viewer there is no difference between some process being run or a link being followed by the linkserver. Of course, these scripts may cause new messages to be sent back to the viewer, to change its presentation in some way.",{"_31":2714,"_33":2715},[],{"_35":160,"_37":2716,"_39":481,"_41":2717,"_66":2718,"_68":2719,"_70":69},"RgoBSImr",{},[],"Client End Scripts. These are scripts that are sent to the viewer by the linkserver. In general they are either sent as part of a LocSpec in order to identify an anchor, or they are sent as a process which the viewer will be expected to run, for example in order to change the presentation of the data in some way. OHP must provide support for such scripts if the viewer wishes to use them.",{"_35":160,"_37":2721,"_39":481,"_41":2722,"_66":2723,"_68":2724,"_70":69},"r0bupa2X",{"_273":2113},[],"Scripts play an important part in some hypermedia systems (e.g. Hypercard and Multicard) , and are hardly used in others. Scripts may be classified into two types:",{"_31":2726,"_33":2727},[],{"_35":160,"_37":2728,"_39":481,"_41":2729,"_66":2730,"_68":2731,"_70":69},"yBQ4QBzn",{},[],"The message being foreseen to deal with these scripts is the Interpret message. It is sent fom the LinkService to the Viewer in order to execute a script at the Viewer. If the script is not executable or any other type of error occurs this message should be answered by the Viewer with an \"error\" message.",{"_31":2733,"_33":2734},[],{"_35":2026,"_37":2735,"_39":481,"_41":2736,"_66":2737,"_68":2738,"_70":69},"iRPDRJxk",{"_2029":69},[],"\n\\MessId MS_Interpret_OHP_1.0\n\\Subject \"Interpret\"\n\\ScriptLanguage language, e.g. Perl, JavaScript, ...\n\\Data the actual script\n\\SessionId \n\\UserId \n",{"_35":870,"_37":2740,"_39":481,"_41":2741,"_66":2742,"_68":2747,"_70":69},"vjEa2vNL",{"_273":323},[2743],{"_35":166,"_167":2744,"_169":2745,"_41":2746,"_70":69},[137],[985],{},"Message \"Interpret\"",{"_31":2749,"_33":2764},[2750,2757],{"_31":2751,"_33":2752},[],{"_35":160,"_37":2753,"_39":481,"_41":2754,"_66":2755,"_68":2756,"_70":69},"3HqV6fo0",{},[],"The LinkService might independently inform the Viewer about new anchors. It can do so by sending \"NewAnchor\" messages.",{"_31":2758,"_33":2759},[],{"_35":2026,"_37":2760,"_39":481,"_41":2761,"_66":2762,"_68":2763,"_70":69},"IEnHCMk5",{"_2029":69},[],"\n\\MessId MS_NewAnchor_OHP_1.0\n\\Subject \"NewAnchor\"\n\\Data {\\AnchorId \\LocSpec\n \\Direction {\"AtoB\" | \"bidirectional\"}\n \\Presentation \\Service}\n\\SessionId \n\\UserId \n",{"_35":870,"_37":2765,"_39":481,"_41":2766,"_66":2767,"_68":2772,"_70":69},"f2YGyWEk",{"_273":323},[2768],{"_35":166,"_167":2769,"_169":2770,"_41":2771,"_70":69},[137],[985],{},"Message \"NewAnchor\"",{"_31":2774,"_33":2789},[2775,2782],{"_31":2776,"_33":2777},[],{"_35":160,"_37":2778,"_39":481,"_41":2779,"_66":2780,"_68":2781,"_70":69},"ujzhFYrr",{},[],"This message is sent by the LinkService to a node that it wishes to automatically close e.g. in order to free a lock on a document.",{"_31":2783,"_33":2784},[],{"_35":2026,"_37":2785,"_39":481,"_41":2786,"_66":2787,"_68":2788,"_70":69},"atDUU23R",{"_2029":69},[],"\n\\MessId MV_CloseNode_OHP_1.0\n\\Subject \"CloseNode\"\n\\NodeId \n\\UpdateNode {\"True\" | \"False\"}\n\\SessionId \n\\UserId \n",{"_35":870,"_37":2790,"_39":481,"_41":2791,"_66":2792,"_68":2797,"_70":69},"pakn40CZ",{"_273":323},[2793],{"_35":166,"_167":2794,"_169":2795,"_41":2796,"_70":69},[137],[985],{},"Message \"CloseNode\"",{"_31":2799,"_33":2800},[],{"_35":160,"_37":2801,"_39":481,"_41":2802,"_66":2803,"_68":2804,"_70":69},"ZTkGolV3",{},[],"The application is then responsible for closing the node itself, ensuring that it has updated any anchors and its contents if required by the UpdateNode tag. In case of any errors the Viewer should send back an error message.",{"_31":2806,"_33":2821},[2807,2814],{"_31":2808,"_33":2809},[],{"_35":160,"_37":2810,"_39":481,"_41":2811,"_66":2812,"_68":2813,"_70":69},"Ty5dbshe",{},[],"The \"Error\" message might be sent by any component. It is composed of the following structure:",{"_31":2815,"_33":2816},[],{"_35":2026,"_37":2817,"_39":481,"_41":2818,"_66":2819,"_68":2820,"_70":69},"fwtNrTkV",{"_2029":69},[],"\n\\MessId M_Error_OHP_1.0\n\\Subject \"Error\"\n\\MessageId Id of message that caused the error\n\\ErrorSubject the type of error that occurred\n\\ErrorMessage the actual error string\n\\SessionId \n\\UserId \n",{"_35":870,"_37":2822,"_39":481,"_41":2823,"_66":2824,"_68":2830,"_70":69},"WaqN8FCL",{"_273":323},[2825],{"_35":166,"_167":2826,"_169":2827,"_41":2829,"_70":69},[137],[2828],15,{},"Message \"Error\"",{"_35":870,"_37":2832,"_39":481,"_41":2833,"_66":2834,"_68":2835,"_70":69},"2NAngyvB",{"_273":323},[],"6.3 Overview of Messages",{"_31":2837,"_33":3062},[2838,2845,2852,2873,2880,2887,2894,2901,2908,2915,2922,2943,2971,2978,2999,3020,3041],{"_31":2839,"_33":2840},[],{"_35":160,"_37":2841,"_39":481,"_41":2842,"_66":2843,"_68":2844,"_70":69},"-sv7Jyyt",{},[],"The definition of the location specifications has been quite a controversial issue (see Thread \"opaque locspecs\"). The two main camps being the \"opaque\" people on one side and the \"HyTime\" people on the other end of the spectrum. The argument towards opaque location specification is that for the LinkService location specifications should be opaque because the LinkService does not actually deal with them but rather wants to handle them as uninterpreted byte blocks. The HyTime (HyTime; 1992) followers on the other hand argue that at some point you actually have to have a specification so that an application is able to locate a specific position within a document's multimedia content. And if you have to define it use an existing standard that has been developed in order to deal with location specifications in an abstract, platform independent way.",{"_31":2846,"_33":2847},[],{"_35":160,"_37":2848,"_39":481,"_41":2849,"_66":2850,"_68":2851,"_70":69},"Y7iCcrYa",{},[],"We have learned from both viewpoints and have concluded that both are right. Therfore, we do not treat location specifcations as opqaue but we allow components to do so by simply ignoring the specifications.",{"_31":2853,"_33":2868},[2854,2861],{"_31":2855,"_33":2856},[],{"_35":160,"_37":2857,"_39":481,"_41":2858,"_66":2859,"_68":2860,"_70":69},"eHqDirbl",{},[],"A full HyTime implementation was considered to put too much onus on the application and also would be rather difficult to implement in a macro-like language. We thus agreed on a subset of location specifications as defined in HyTime.",{"_31":2862,"_33":2863},[],{"_35":160,"_37":2864,"_39":481,"_41":2865,"_66":2866,"_68":2867,"_70":69},"CsncpwYY",{},[],"The protocol is assumed to develop, thus in a first step the focus is on establishing the protocol and later on improving and enhancing it. However, we are convinced that without a basic agreement on the location specifications real interoperability between viewers is not possible.",{"_35":160,"_37":2869,"_39":481,"_41":2870,"_66":2871,"_68":2872,"_70":69},"eIzI5rNm",{"_273":274},[],"A number of additionally criteria have been influencing our decision for the current definition of location specifiers:",{"_31":2874,"_33":2875},[],{"_35":160,"_37":2876,"_39":481,"_41":2877,"_66":2878,"_68":2879,"_70":69},"If8Wj5Ib",{},[],"As an example let us take the simplest data type, e.g. ASCII text. Most systems have developed similar fairly rich methods of locating strings. The location specification should include standards for these methods. Later, we might extend standards for such things as pictures, formatted text, videos etc. But opaque types will always be allowed and supported.",{"_31":2881,"_33":2882},[],{"_35":160,"_37":2883,"_39":481,"_41":2884,"_66":2885,"_68":2886,"_70":69},"50Bbvigq",{},[],"We also would like to stress the point that standarisation of location specifications is only partially subject to OHP. This can be compared to the situation with the document management protocol: strictly speaking this should not be part of the definition of OHP; however, if OHP should be really useful there have to be some common assumptions about both location specifications and document management functionality. For the current version of OHP we therefore provide these features so that OHP as a protocol can be implemented.",{"_31":2888,"_33":2889},[],{"_35":160,"_37":2890,"_39":481,"_41":2891,"_66":2892,"_68":2893,"_70":69},"e3STn_1e",{},[],"Now that we have explained in general our decisions we are able to define location specifications as part of OHP.",{"_31":2895,"_33":2896},[],{"_35":2026,"_37":2897,"_39":481,"_41":2898,"_66":2899,"_68":2900,"_70":69},"x2E-USY-",{"_2029":69},[],"LocSpec =\n\\ContentType type, e.g., ASCII, binary\n\\Content Mime encoded text string\n\\LocData Loc\n",{"_31":2902,"_33":2903},[],{"_35":160,"_37":2904,"_39":481,"_41":2905,"_66":2906,"_68":2907,"_70":69},"1DCuoHkZ",{},[],"Location specification consist of a content type, the content itsef as well as the actual location data. LocData is defined as",{"_31":2909,"_33":2910},[],{"_35":2026,"_37":2911,"_39":481,"_41":2912,"_66":2913,"_68":2914,"_70":69},"Gxaoggfi",{"_2029":69},[],"Loc = NameLoc | DataLoc | TreeLoc | PathLoc | ScriptLoc | NALoc\n",{"_31":2916,"_33":2917},[],{"_35":160,"_37":2918,"_39":481,"_41":2919,"_66":2920,"_68":2921,"_70":69},"hLgvMjbI",{},[],"In the sequel we will explain these different basic types of location specifications. Again, it is up to the developer to introduce his own additional location specification or to add additional tags where necessry for specific applications. For most cases though, the proposed set of location specifications should be sufficient.",{"_31":2923,"_33":2938},[2924,2931],{"_31":2925,"_33":2926},[],{"_35":160,"_37":2927,"_39":481,"_41":2928,"_66":2929,"_68":2930,"_70":69},"LyBEqS8m",{},[],"Name space locations are used to reference an object by its name. Names are expressed in OHP by NodeIds so the defintion of NameLoc is as follows:",{"_31":2932,"_33":2933},[],{"_35":2026,"_37":2934,"_39":481,"_41":2935,"_66":2936,"_68":2937,"_70":69},"KVVIOp5S",{"_2029":69},[],"NameLoc =\n \\LocType \"NameLoc\"\n \\NodeId \n",{"_35":870,"_37":2939,"_39":481,"_41":2940,"_66":2941,"_68":2942,"_70":69},"X0EjPCyX",{"_273":323},[],"Name Space Locations",{"_31":2944,"_33":2966},[2945,2952,2959],{"_31":2946,"_33":2947},[],{"_35":160,"_37":2948,"_39":481,"_41":2949,"_66":2950,"_68":2951,"_70":69},"mbiacGB-",{},[],"So-called data locations are coordinate locations, i.e., objects are addressed by their relative position to another object. DataLocs will be heavily used by OHP as most systems define anchors by relative positioning, for instance by keeping an offset. In order to know how this dimension specification should be interpreted, i.e. to get its data type, a quantum tag is defined. Count list follows the HyTime semantics of defining a dimenstion list. In particular, two markers define beginning and end of a node on an axis thus resulting in (number of axes * 2) markers.",{"_31":2953,"_33":2954},[],{"_35":160,"_37":2955,"_39":481,"_41":2956,"_66":2957,"_68":2958,"_70":69},"7bTghDQH",{},[],"A reverse counter is kept in order to do cross checking of validity of anchors. In case the expected object still can not be found an overrun behaviour can be specified: the error can simply be ignored, the markers can be truncated to the last unit on the axis or an error can be raised.",{"_31":2960,"_33":2961},[],{"_35":160,"_37":2962,"_39":481,"_41":2963,"_66":2964,"_68":2965,"_70":69},"oeFqmqou",{},[],"The HyTime time quantum \"utc\" expects items in the form yyyy-mm-dd hh:mm:ss.decimal, e.g., 1997-06- 06 17:59:22.6122.",{"_35":870,"_37":2967,"_39":481,"_41":2968,"_66":2969,"_68":2970,"_70":69},"HJkHeMQB",{"_273":323},[],"Data Locations",{"_31":2972,"_33":2973},[],{"_35":2026,"_37":2974,"_39":481,"_41":2975,"_66":2976,"_68":2977,"_70":69},"GD0GfhxA",{"_2029":69},[],"DataLoc =\n \\LocType \"DataLoc\"\n \\NodeId \n \\Quantum \"string\" | \"int\" | \"byte\" | \"utc\"\n \\CountList list of Strings being interpreted by the viewer\n \\RevCountList list of Strings being interpreted by the viewer\n \\Overrun \"ignore\" | \"error\" | \"trunc\" overrun attribute\n",{"_31":2979,"_33":2994},[2980,2987],{"_31":2981,"_33":2982},[],{"_35":160,"_37":2983,"_39":481,"_41":2984,"_66":2985,"_68":2986,"_70":69},"_iOk0BtS",{},[],"Tree locations can be used for addressing a single object within a tree. The addressing is done in a way that on each level of the tree an object is selected by its position. These position numbers are expressed in CountList. For example a count list of \"1 2 3\" applied to a NodeId referencing a book would get the third section of the second chapter of the book (assuming that a book has a structure with chapters and sections).",{"_31":2988,"_33":2989},[],{"_35":2026,"_37":2990,"_39":481,"_41":2991,"_66":2992,"_68":2993,"_70":69},"kOQQKZ7r",{"_2029":69},[],"TreeLoc =\n \\LocType \"TreeLoc\"\n \\NodeId \n \\Overrun \"ignore\" | \"error\" | \"trunc\"\n \\CountList list of numbers",{"_35":870,"_37":2995,"_39":481,"_41":2996,"_66":2997,"_68":2998,"_70":69},"386Z2vpd",{"_273":323},[],"Tree Locations",{"_31":3000,"_33":3015},[3001,3008],{"_31":3002,"_33":3003},[],{"_35":160,"_37":3004,"_39":481,"_41":3005,"_66":3006,"_68":3007,"_70":69},"JkWjxXNk",{},[],"As opposed to tree locations path locations are used to address a range of nodes by a path. This is done by addressing a tree as though it were a matrix in which the rows are the levels of the tree and the columns are the paths. Therefore the count list of a path location consists of an even number of pairs: the first pair identifies the columns (i.e. the paths to the leaves) and the second pair selects the rows.",{"_31":3009,"_33":3010},[],{"_35":2026,"_37":3011,"_39":481,"_41":3012,"_66":3013,"_68":3014,"_70":69},"_9OeIVpX",{"_2029":69},[],"PathLoc =\n \\LocType \"PathLoc\"\n \\NodeId \n \\Overrun \"ignore\" | \"error\" | \"trunc\"\n \\CountList list of numbers",{"_35":870,"_37":3016,"_39":481,"_41":3017,"_66":3018,"_68":3019,"_70":69},"D3S_3Z7W",{"_273":323},[],"Path Locations",{"_31":3021,"_33":3036},[3022,3029],{"_31":3023,"_33":3024},[],{"_35":160,"_37":3025,"_39":481,"_41":3026,"_66":3027,"_68":3028,"_70":69},"VtgFr93a",{},[],"OHP does not define a specific query mechanism for addressing locations (as thus for instance HyTime with the standard DSSSL Query Language, SDQ). However, by allowing script locations we define a way for those Hypermedia systems that use scripts to identify and address locations at the client's side.",{"_31":3030,"_33":3031},[],{"_35":2026,"_37":3032,"_39":481,"_41":3033,"_66":3034,"_68":3035,"_70":69},"mgGu8oKA",{"_2029":69},[],"ScriptLoc =\n \\LocType \"ScriptLoc\"\n \\Script viewer executable script\n",{"_35":870,"_37":3037,"_39":481,"_41":3038,"_66":3039,"_68":3040,"_70":69},"RIMeK5bb",{"_273":323},[],"Script Locations",{"_31":3042,"_33":3057},[3043,3050],{"_31":3044,"_33":3045},[],{"_35":160,"_37":3046,"_39":481,"_41":3047,"_66":3048,"_68":3049,"_70":69},"756uf_OB",{},[],"An idea borrowed from HyTime is to address data that is currently not accessible. This could be a printed book which is not available on-line, a radio broadcast or even a person or an organization. The point is that it might in some cases make sense to reference these nodes without having a Viewer for them. Instead, the Viewer could display a notification string, stating for example where to find a book in a shelf in a library. We call this location specification NALoc for \"not accessible\" location.",{"_31":3051,"_33":3052},[],{"_35":2026,"_37":3053,"_39":481,"_41":3054,"_66":3055,"_68":3056,"_70":69},"6JHFA1C2",{"_2029":69},[],"NALoc =\n \\LocType \"NALoc\"\n \\Loc string as description of the object and its physical location\n",{"_35":870,"_37":3058,"_39":481,"_41":3059,"_66":3060,"_68":3061,"_70":69},"zTZA81LN",{"_273":323},[],"Inaccessible Locations",{"_35":870,"_37":3063,"_39":481,"_41":3064,"_66":3065,"_68":3066,"_70":69},"VJYfBroP",{"_273":323},[],"6.4 Location Specifications",{"_31":3068,"_33":3145},[3069,3076,3083,3090,3097,3104,3111,3118,3131,3138],{"_31":3070,"_33":3071},[],{"_35":160,"_37":3072,"_39":481,"_41":3073,"_66":3074,"_68":3075,"_70":69},"ScD4TpLm",{},[],"Many systems incorporate the possibility of displaying persistent selections in different ways. For example, persistent selections in text might be coloured blue, or some other colour, and areas of bitmaps might be shaded, raised or outlined; some systems support buttons that are not shown, or are only shown when the pointer is over them. In general this is a user choice, and it applies to all the persistent selections in the view, so may be a setting on the viewer that is completely independent of the link service.",{"_31":3077,"_33":3078},[],{"_35":160,"_37":3079,"_39":481,"_41":3080,"_66":3081,"_68":3082,"_70":69},"igq_Dchn",{},[],"However, there are cases where an author may wish particular persistent selections to show in some way that is different from others. In this case it is possible for the viewer to allow the specification of some particular presentation of the selection, and to store this along with the LocSpec, so that when it is viewed later, it will have the desired appearance. If this were the only requirement, the syntax and semantics of the presentation specifier would belong only to the viewer.",{"_31":3084,"_33":3085},[],{"_35":160,"_37":3086,"_39":481,"_41":3087,"_66":3088,"_68":3089,"_70":69},"1pGwRKCN",{},[],"Unfortunately, there are many cases where the link service may wish, as the result of some script, to change the presentation, and the linkservice will not know the presentation unless it is part of the standard.",{"_31":3091,"_33":3092},[],{"_35":160,"_37":3093,"_39":481,"_41":3094,"_66":3095,"_68":3096,"_70":69},"LvY-Z7vY",{},[],"For the purpose of this version of the protocol we suggest that the information about presentation is kept Viewer specific. i.e. the Viewer may ask to store any presentation information in any form that it chooses, and the Viewer will interpret this data at a later stage when asked to present the data again.",{"_31":3098,"_33":3099},[],{"_35":160,"_37":3100,"_39":481,"_41":3101,"_66":3102,"_68":3103,"_70":69},"G8FJ0Kud",{},[],"The consequence of this policy will be that the LinkService will not be able to communicate to the Viewer that it should change any presentation (e.g. as the result of a script) since it will not know the syntax of the presentation tag for this particular Viewer.",{"_31":3105,"_33":3106},[],{"_35":160,"_37":3107,"_39":481,"_41":3108,"_66":3109,"_68":3110,"_70":69},"IRYielXq",{},[],"We are aware that strictly speaking presentation styles should not be defined within OHP (Anderson, 1997). However, as is true for the document management part and also for the location specifications, in order to make OHP really useable in the first phase a standardised agreed way of expressing presentation specifics has to be found.",{"_31":3112,"_33":3113},[],{"_35":2026,"_37":3114,"_39":481,"_41":3115,"_66":3116,"_68":3117,"_70":69},"3yhJohZm",{"_2029":69},[],"\\Presentation [\\Colour colour][\\style style]\n [\\visibility \"true\"| \"false\"]\n",{"_31":3119,"_33":3120},[],{"_35":160,"_37":3121,"_39":481,"_41":3122,"_66":3123,"_68":3130,"_70":69},"WWoT_Wi1",{},[3124],{"_35":166,"_167":3125,"_169":3127,"_41":3129,"_70":69},[3126],263,[3128],268,{},"Following the original proposal we suggest a triplet of colour, style, visibility, each of which is optional. The above defintion allows us to only put these things if we have them, and we could also add other tags if needed. We will define some tag values which will be understood.",{"_31":3132,"_33":3133},[],{"_35":160,"_37":3134,"_39":481,"_41":3135,"_66":3136,"_68":3137,"_70":69},"ea9PKFVP",{},[],"We assume that the eight primary computer colours are supported, i.e. blue, cyan, green, magenta, orange, pink, red and yellow.",{"_31":3139,"_33":3140},[],{"_35":160,"_37":3141,"_39":481,"_41":3142,"_66":3143,"_68":3144,"_70":69},"MNKL9jkv",{},[],"As minimal subset of styles we define flashing, bold, italic, outlined and shaded.",{"_35":870,"_37":3146,"_39":481,"_41":3147,"_66":3148,"_68":3149,"_70":69},"H4q3KtZO",{"_273":323},[],"6.5 Presentation Specification",{"_35":870,"_37":3151,"_39":481,"_41":3152,"_66":3153,"_68":3154,"_70":69},"JB-7sOxa",{"_273":323},[],"6. Definitions",{"_31":3156,"_33":3201},[3157,3164],{"_31":3158,"_33":3159},[],{"_35":160,"_37":3160,"_39":481,"_41":3161,"_66":3162,"_68":3163,"_70":69},"FCF4FsG7",{},[],"In this section we consider, by reference to some different types of hypermedia viewers, the way these applications might use the OHP protocol. In order to allow readers to 'play' with OHP and to better visualize the communiction process we have developed a small Java applet that should help in understanding OHP.",{"_31":3165,"_33":3192},[3166,3173],{"_31":3167,"_33":3168},[],{"_35":160,"_37":3169,"_39":481,"_41":3170,"_66":3171,"_68":3172,"_70":69},"o8LiLZZQ",{},[],"The following simple applet is based on the assumptions we have made about the components being involved in an OHP scenario. On the OHP level we thus only have two components, Viewer and LinkService, that talk OHP to each other. The communication layer is not shown in the applet.",{"_31":3174,"_33":3187},[3175],{"_31":3176,"_33":3177},[],{"_35":160,"_37":3178,"_39":481,"_41":3179,"_66":3180,"_68":3186,"_70":69},"4NJmJYvh",{},[3181],{"_35":166,"_167":3182,"_169":3183,"_41":3185,"_70":69},[137],[3184],43,{},"Fig.: Java Applet allowing to play with OHP",{"_35":160,"_37":3188,"_39":481,"_41":3189,"_66":3190,"_68":3191,"_70":69},"2RWgWbpR",{"_273":323},[],"In order to play with OHP select a scenario and walk through it by pressing 'start'.",{"_35":870,"_37":3193,"_39":481,"_41":3194,"_66":3195,"_68":3200,"_70":69},"37lVPsn6",{"_273":323},[3196],{"_35":166,"_167":3197,"_169":3198,"_41":3199,"_70":69},[137],[1542],{},"Try out OHP!",{"_35":870,"_37":3202,"_39":481,"_41":3203,"_66":3204,"_68":3205,"_70":69},"-Ue96qsv",{"_273":323},[],"7. Example Scenarios",{"_31":3207,"_33":3269},[3208,3243],{"_31":3209,"_33":3238},[3210,3217,3224,3231],{"_31":3211,"_33":3212},[],{"_35":160,"_37":3213,"_39":481,"_41":3214,"_66":3215,"_68":3216,"_70":69},"QhYPj_is",{},[],"The World-Wide Web Consortium proposes a standardised way to extend the HyperText Transfer Protocol. This extension is called Protocol Extension Protocol (PEP, Nielsen, 1997).",{"_31":3218,"_33":3219},[],{"_35":160,"_37":3220,"_39":481,"_41":3221,"_66":3222,"_68":3223,"_70":69},"e-uN6rte",{},[],"PEP should be used for situations where applications require more facilities than the standard version of HTTP provides, from distributed authoring, collaboration and printing, to various remote procedure call mechanisms.",{"_31":3225,"_33":3226},[],{"_35":160,"_37":3227,"_39":481,"_41":3228,"_66":3229,"_68":3230,"_70":69},"ix5YBm7l",{},[],"The Protocol Extension Protocol (PEP) is an extension mechanism designed to address the tension between private agreement and public specification and to accommodate extension of HTTP clients and servers by software components. The PEP mechanism is to associate each extension with a URI, and use a few new header fields to carry the extension identifier and related information from HTTP clients, through proxies and intermediaries, to servers, and back again.",{"_31":3232,"_33":3233},[],{"_35":160,"_37":3234,"_39":481,"_41":3235,"_66":3236,"_68":3237,"_70":69},"WNboOKrN",{},[],"From an OHP point of view PEP could be used in the communications layer which is represented by the SessionManager component. OHP itself however, is on a higher level and its focus is different to that of PEP being based on HTTP.",{"_35":870,"_37":3239,"_39":481,"_41":3240,"_66":3241,"_68":3242,"_70":69},"42Lav33m",{"_273":323},[],"8.1 Protocol Extension Protocol (PEP)",{"_31":3244,"_33":3264},[3245,3252],{"_31":3246,"_33":3247},[],{"_35":160,"_37":3248,"_39":481,"_41":3249,"_66":3250,"_68":3251,"_70":69},"vO4W7rgH",{},[],"OpenDoc is a multi-platform component-based architecture, based around CORBA. OpenDoc uses compound documents, where the data in each component is viewed and accessed by means of \"part editors\". OpenDoc assigns the correct editor to handle each different data type, looking first at user preferences, and failing that, making an intelligent decision based on the data type, and its knowledge of the available editors. The part editors share windows, menus and other resources within a document. OpenDoc provides a highly versatile persistent storage system known as Bento, which allows multiple part editors to share a single document file. The Bento storage units and mechanisms are also used for clipboard transfers, drag-and-drop, and linking between parts, documents and/or networks.",{"_31":3253,"_33":3254},[],{"_35":160,"_37":3255,"_39":481,"_41":3256,"_66":3257,"_68":3263,"_70":69},"EgxRK8Cl",{},[3258],{"_35":919,"_167":3259,"_169":3260,"_41":3262,"_70":69},[1556],[3261],49,{},"OpenDoc includes the Open Scripting Architecture - a highly versatile mechanism that includes an Apple Event Model (AEOM) style communication architecture. Consequently the same kind of Shims that would work with the AEOM would work with properly built OpenDoc part editors, and hence with OpenDoc applications. OpenDoc is a multi-platform architecture, and if it is successful in establishing itself the implications are significant.",{"_35":870,"_37":3265,"_39":481,"_41":3266,"_66":3267,"_68":3268,"_70":69},"XaNrRqy-",{"_273":323},[],"8.2 OpenDoc",{"_35":870,"_37":3270,"_39":481,"_41":3271,"_66":3272,"_68":3273,"_70":69},"RAUOqF-2",{"_273":323},[],"8. Related Work",{"_31":3275,"_33":3297},[3276],{"_31":3277,"_33":3292},[3278,3285],{"_31":3279,"_33":3280},[],{"_35":160,"_37":3281,"_39":481,"_41":3282,"_66":3283,"_68":3284,"_70":69},"8JlLnIPQ",{},[],"Collaboration",{"_31":3286,"_33":3287},[],{"_35":160,"_37":3288,"_39":481,"_41":3289,"_66":3290,"_68":3291,"_70":69},"NU-Wvt11",{},[],"Transaction Semantics",{"_35":160,"_37":3293,"_39":481,"_41":3294,"_66":3295,"_68":3296,"_70":69},"YmQRi_fm",{"_273":274},[],"We sum up what we have proposed, conclude. List of open issues:",{"_35":870,"_37":3298,"_39":481,"_41":3299,"_66":3300,"_68":3301,"_70":69},"keTzgVzJ",{"_273":323},[],"9. Summary and Conclusion ",{"_31":3303,"_33":3311},[3304],{"_31":3305,"_33":3306},[],{"_35":160,"_37":3307,"_39":481,"_41":3308,"_66":3309,"_68":3310,"_70":69},"ac-C2x25",{},[],"The OHS community, all that have contributed in any form. Special thanks to Pete Nürnberg, Ken Anderson, Richard Taylor.",{"_35":870,"_37":3312,"_39":481,"_41":3313,"_66":3314,"_68":3315,"_70":69},"hvS6KMvc",{"_273":323},[],"Acknowledgements",{"_31":3317,"_33":3491},[3318,3329,3342,3354,3366,3379,3392,3399,3412,3423,3430,3437,3444,3457,3468,3480],{"_31":3319,"_33":3320},[],{"_35":160,"_37":3321,"_39":481,"_41":3322,"_66":3323,"_68":3328,"_70":69},"LuY0cf8c",{},[3324],{"_35":919,"_167":3325,"_169":3326,"_41":3327,"_70":69},[171],[1414],{},"Kenneth M. A. A Critique of the Open Hypermedia Protocol. 3rd Workshop on Open Hypermedia Systems, Southampton, April 1997. Available as http://www.daimi.aau.dk/~kock/OHS- HT97/Papers/anderson.html [1997 June 20].",{"_31":3330,"_33":3331},[],{"_35":160,"_37":3332,"_39":481,"_41":3333,"_66":3334,"_68":3341,"_70":69},"duzL0LaI",{},[3335],{"_35":919,"_167":3336,"_169":3338,"_41":3340,"_70":69},[3337],37,[3339],117,{},"Davis, H.C., Knight, S.K. & Hall, W. Light Hypermedia Link Services: A Study in Third Party Application Integration. In: The ACM Conference on Hypermedia Technology, ECHT '94 Proceedings. pp 41-50. ACM. Sept. 1994.",{"_31":3343,"_33":3344},[],{"_35":160,"_37":3345,"_39":481,"_41":3346,"_66":3347,"_68":3353,"_70":69},"VwZ99rsB",{},[3348],{"_35":919,"_167":3349,"_169":3350,"_41":3352,"_70":69},[2355],[3351],142,{},"Davis, H., Lewis, A., Rizk, A. OHP: A Draft Proposal for a Standard Open Hypermedia Protocol (Levels 0 and 1: Revision 1.2 - 13th March. 1996). 2nd Workshop on Open Hypermedia Systems, Washington, March 1996. Available as http://www.ecs.soton.ac.uk/~hcd/protweb.htm [1997 June 20].",{"_31":3355,"_33":3356},[],{"_35":160,"_37":3357,"_39":481,"_41":3358,"_66":3359,"_68":3365,"_70":69},"g5OSzN2T",{},[3360],{"_35":919,"_167":3361,"_169":3362,"_41":3364,"_70":69},[1464],[3363],26,{},"Davis, H.: Channels in OHP. Thread in OHS Mailing List (1997 June 6) Available as http://www.csdl.tamu.edu/ohs/archive/0032.html [1997 June 20].",{"_31":3367,"_33":3368},[],{"_35":160,"_37":3369,"_39":481,"_41":3370,"_66":3371,"_68":3378,"_70":69},"XG99Npjy",{},[3372],{"_35":919,"_167":3373,"_169":3375,"_41":3377,"_70":69},[3374],28,[3376],125,{},"Goose S., Lewis A., Hugh D. OHRA: Towards an Open Hypermedia Reference Architecture and a Migration Path for Existing Systems. 3rd Workshop on Open Hypermedia Systems, Southampton, April 1997. Available as http://www.daimi.aau.dk/~kock/OHS-HT97/Papers/goose.html [1997 June 20].",{"_31":3380,"_33":3381},[],{"_35":160,"_37":3382,"_39":481,"_41":3383,"_66":3384,"_68":3391,"_70":69},"FXhx1SFy",{},[3385],{"_35":919,"_167":3386,"_169":3387,"_41":3390,"_70":69},[3363,1097],[3388,3389],82,202,{},"Grønbæk, K. & Trigg, R.H. Design Issues for a Dexter-Based Hypermedia System. In: D. Lucarella, J. Nanard, M. Nanard, P. Paolini. eds. The Proceedings of the ACM Conference on Hypertext, ECHT '92 Milano, pp 191-200. ACM Press. Nov. 1992",{"_31":3393,"_33":3394},[],{"_35":160,"_37":3395,"_39":481,"_41":3396,"_66":3397,"_68":3398,"_70":69},"cbJVaiBI",{},[],"ISO - International Organization for Standardization: Information Technology - Hypermedia/Time-based Structuring Language (HyTime), ISO/IEC 10744, 1992.",{"_31":3400,"_33":3401},[],{"_35":160,"_37":3402,"_39":481,"_41":3403,"_66":3404,"_68":3411,"_70":69},"p3P90Mzo",{},[3405],{"_35":919,"_167":3406,"_169":3408,"_41":3410,"_70":69},[3407],29,[3409],91,{},"Kacmar, C.J. & Leggett, J.J. PROXHY: A Process-Oriented Extensible Hypertext Architecture. ACM Trans. on Information Systems, 9(4) pp 299-419. Oct. 1991.",{"_31":3413,"_33":3414},[],{"_35":160,"_37":3415,"_39":481,"_41":3416,"_66":3417,"_68":3422,"_70":69},"PlK5vrpO",{},[3418],{"_35":919,"_167":3419,"_169":3420,"_41":3421,"_70":69},[2828],[1573],{},"Nürnberg, P.: opaque locspecs. Thread in OHS Mailing List (1997 April 17) Available as http://www.csdl.tamu.edu/ohs/archive/0023.html [1997 June 20].",{"_31":3424,"_33":3425},[],{"_35":160,"_37":3426,"_39":481,"_41":3427,"_66":3428,"_68":3429,"_70":69},"AEWVo2uC",{},[],"Open Document Management API (ODMA): Open Document Management API Version 1.5. Available as http://www.aiim.org/odma/odma15.htm [1997 June 20].",{"_31":3431,"_33":3432},[],{"_35":160,"_37":3433,"_39":481,"_41":3434,"_66":3435,"_68":3436,"_70":69},"TOSNHKWS",{},[],"PEP - an Extension Mechanism for HTTP: W3C Working Draft 28 April 1997. Edited by Henrik Frystyk Nielsen. Available as http://www.w3.org/TR/WD-http-pep-970428 [1997 June 20].",{"_31":3438,"_33":3439},[],{"_35":160,"_37":3440,"_39":481,"_41":3441,"_66":3442,"_68":3443,"_70":69},"IF9prJIl",{},[],"Reich, S.: How OHP's LocSpecs could benefit from ISO/IEC 10744. 3rd Workshop on Open Hypermedia Systems, Southampton, April 1997. Available as http://www.daimi.aau.dk/~kock/OHS- HT97/Papers/reich.ps [1997 June 20].",{"_31":3445,"_33":3446},[],{"_35":160,"_37":3447,"_39":481,"_41":3448,"_66":3449,"_68":3456,"_70":69},"Gh_M3Kv8",{},[3450],{"_35":919,"_167":3451,"_169":3452,"_41":3455,"_70":69},[1011,3339],[3453,3454],58,184,{},"Rizk, A. & Sauter, L. Multicard: An Open Hypermedia System. In: D. Lucarella, J. Nanard, M. Nanard, P. Paolini. eds. The Proceedings of the ACM Conference on Hypertext, ECHT '92 Milano, Italy, December 1992, pp 181-190. ACM Press. 1992",{"_31":3458,"_33":3459},[],{"_35":160,"_37":3460,"_39":481,"_41":3461,"_66":3462,"_68":3467,"_70":69},"hzD1fdKj",{},[3463],{"_35":919,"_167":3464,"_169":3465,"_41":3466,"_70":69},[171],[1117],{},"Taylor, R. N. Response: A Draft Proposal for a Standard Open Hypermedia Protocol. 2nd Workshop on Open Hypermedia Systems, Washington, March 1996. Available as ?????????????????? [1997 June 20].",{"_31":3469,"_33":3470},[],{"_35":160,"_37":3471,"_39":481,"_41":3472,"_66":3473,"_68":3479,"_70":69},"Hug8UDTF",{},[3474],{"_35":919,"_167":3475,"_169":3477,"_41":3478,"_70":69},[3476],33,[3376],{},"Wiil, U.K & Østerbye, K. (eds.). The Proceedings of the ECHT '94 Workshop on Open Hypermedia Systems, Edinburgh, Sept. 1994. Technical Report R-94-2038. Aalborg University. Oct. 1994.",{"_31":3481,"_33":3482},[],{"_35":160,"_37":3483,"_39":481,"_41":3484,"_66":3485,"_68":3490,"_70":69},"2nSqQAnH",{},[3486],{"_35":919,"_167":3487,"_169":3488,"_41":3489,"_70":69},[2531],[185],{},"Wiil, U.K & Leggett, J. The HyperDisco Approach to Open Hypermedia Systems. In: The Proceedings of the ACM Conference on Hypertext '96, Washington D.C., pp 140-148. ACM Press. March 1996. An OHP application must also provide an interface to allow anchors to be updated e.g. after document editing.",{"_35":870,"_37":3492,"_39":481,"_41":3493,"_66":3494,"_68":3495,"_70":69},"QAYEeiF7",{"_273":323},[],"References",[279,53],"/records/ohp-open-hypermedia-protocol","2025-07-07T23:07:11.413Z",{"_82":490},{},{"_37":468,"_95":53,"_54":3502,"_71":471,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,470],1772031973240,[149,468,471],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/ohp-open-hypermedia-protocol\",\"bafy2bzaceb5g2ghhzmslplmaqsyvrz6raz6ub7cuemsnafggjtuntq5jpg67c\"]",{"_110":3507,"_147":5561,"_150":5562},{"_112":3508,"_131":132,"_133":5560,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":3509,"_37":5558},{"_28":3510,"_71":496,"_72":53,"_73":5553,"_54":5554,"_76":505,"_78":5555,"_80":5556,"_84":5557,"_86":506,"_88":89},[3511,3532,3548,3561,3645,3836,3886,4630,4967,5078,5470],{"_31":3512,"_33":3513},[],{"_35":160,"_37":3514,"_39":506,"_41":3515,"_66":3516,"_68":3531,"_70":69},"ZB8af6L_",{},[3517,3521,3525],{"_35":166,"_167":3518,"_169":3519,"_41":3520,"_70":69},[137],[2660],{},{"_35":919,"_167":3522,"_169":3523,"_41":3524,"_70":69},[137],[1700],{},{"_35":204,"_167":3526,"_169":3528,"_41":3529,"_70":3530},[3527],168,[1700],{},"mailto:ajl@ecs.soton.ac.uk","Hugh Davis, Andy Lewis\nThe Multimedia Research Group\nElectronics and Computer Science\nThe University of Southampton\nSouthampton\nUK, SO17 1BJ\nemail hcd@ecs.soton.ac.uk, ajl@ecs.soton.ac.uk",{"_31":3533,"_33":3534},[],{"_35":160,"_37":3535,"_39":506,"_41":3536,"_66":3537,"_68":3547,"_70":69},"RoJ7iSjX",{},[3538,3542],{"_35":166,"_167":3539,"_169":3540,"_41":3541,"_70":69},[137],[1520],{},{"_35":919,"_167":3543,"_169":3544,"_41":3546,"_70":69},[137],[3545],50,{},"Antoine Rizk\nEuroclid\nemail Antoine.Rizk@inria.fr\n",{"_31":3549,"_33":3557},[3550],{"_31":3551,"_33":3552},[],{"_35":160,"_37":3553,"_39":506,"_41":3554,"_66":3555,"_68":3556,"_70":69},"ZlXFOWow",{},[],"This paper describes a proposal for a protocol known as OHP, for communication between applications and hypermedia link services. If hypermedia viewers were written to use this protocol, or third party applications were adapted to use the protocol, then these applications could be used with any link service which adhered to the protocol. The paper proposes the use of shims for converting between the OHP protocol and the linkservice's native protocol.",{"_35":870,"_37":3558,"_39":506,"_41":3559,"_66":3560,"_68":1827,"_70":69},"-pXHwaS0",{"_273":323},[],{"_31":3562,"_33":3640},[3563,3570,3619,3626,3633],{"_31":3564,"_33":3565},[],{"_35":160,"_37":3566,"_39":506,"_41":3567,"_66":3568,"_68":3569,"_70":69},"vb71H-D3",{},[],"In order to introduce this paper we would first like to define what we mean by \"open\" when referring to hypermedia systems. A number of authors (Davis et al., 1992 ; Østerbye, 1996 ) and workshops ( Aßfalg, 1994 ) ( Wiil & Østerbye, 1994 ), have attempted to define the term \"open hypermedia\", and we believe that the following is a reasonable summary of current thinking.",{"_31":3571,"_33":3614},[3572,3579,3586,3593,3600,3607],{"_31":3573,"_33":3574},[],{"_35":160,"_37":3575,"_39":506,"_41":3576,"_66":3577,"_68":3578,"_70":69},"RfiMZajm",{},[],"Size: It should be possible to import new nodes, links, anchors and other hypermedia objects of any limitation, to the size of the objects or to the maximum number of such objects that the system may contain, being imposed by the hypermedia system.",{"_31":3580,"_33":3581},[],{"_35":160,"_37":3582,"_39":506,"_41":3583,"_66":3584,"_68":3585,"_70":69},"P2h_BCAl",{},[],"Data Formats: The system should allow the import and use of any data format, including temporal media.",{"_31":3587,"_33":3588},[],{"_35":160,"_37":3589,"_39":506,"_41":3590,"_66":3591,"_68":3592,"_70":69},"dNN2sa_H",{},[],"Applications: The system should allow any application to access the link service in order to participate in the hypermedia functionality.",{"_31":3594,"_33":3595},[],{"_35":160,"_37":3596,"_39":506,"_41":3597,"_66":3598,"_68":3599,"_70":69},"RJ8W3NJC",{},[],"Data Models: The hypermedia system should not impose a single view of what constitutes a hypermedia data model, but should be configurable and extensible so that new hypermedia data models may be incorporated. It should thus be possible to interoperate with external hypermedia systems, and to exchange data with external systems.",{"_31":3601,"_33":3602},[],{"_35":160,"_37":3603,"_39":506,"_41":3604,"_66":3605,"_68":3606,"_70":69},"Qq8DtCJ9",{},[],"Platforms: It should be possible to implement the system on multiple distributed platforms.",{"_31":3608,"_33":3609},[],{"_35":160,"_37":3610,"_39":506,"_41":3611,"_66":3612,"_68":3613,"_70":69},"TkHHS8qq",{},[],"Users: The system must support multiple users, and allow each user to maintain their own private view of the objects in the system.",{"_35":160,"_37":3615,"_39":506,"_41":3616,"_66":3617,"_68":3618,"_70":69},"6bPmURXZ",{"_273":2113},[],"The term open implies the possibility of importing new objects into a system. A truly open hypermedia system should be open with regard to:",{"_31":3620,"_33":3621},[],{"_35":160,"_37":3622,"_39":506,"_41":3623,"_66":3624,"_68":3625,"_70":69},"lK9JChOJ",{},[],"In this paper we are concerned with enabling applications to make them link service aware, so that users may have access to the full range of hypermedia functionality from their standard desktop environment. Many of the current generation of hypermedia systems such as DHM (Grønbæk & Trigg, 1992 ) HyperDisco ( Wiil, 1996 ), Microcosm ( Davis et al., 1994 ), Multicard ( Rizk & Sauter, 1992 ) and the Texas A&M system prototypes (e.g. Kacmar & Leggett ) have addressed this problem, but so far no standard has emerged due to the different hypertext data models and communication protocols adopted by these systems.",{"_31":3627,"_33":3628},[],{"_35":160,"_37":3629,"_39":506,"_41":3630,"_66":3631,"_68":3632,"_70":69},"vK1BtxRY",{},[],"Unfortunately, linkservice protocols tend to be kept confidential, and are anyway too detailed to form the topic of published papers. However, we have now seen the results of sufficient research in this subject to be able to identify the common themes, and hopefully to abstract the common requirements. This first draft of this protocol leans heavily upon the M2000 protocol (Rizk, 1991 ) developed for use with Multicard, and the Microcosm message model. It is a first attempt at such a standard protocol, and no doubt it will need adapting and will evolve as system designers attempt to map their systems onto the protocol.",{"_31":3634,"_33":3635},[],{"_35":160,"_37":3636,"_39":506,"_41":3637,"_66":3638,"_68":3639,"_70":69},"Hx7rZnoN",{},[],"We should emphasise at this point that all this protocol attempts to provide is a standard method for applications, such as word processors, graphics viewers and drawing programs, to communicate with a link service so that they may offer hypermedia services to their users. This protocol is not an attempt to produce a complete standard for all inter-component communication, such as would be required for the link service to communicate with agents and other service providing components.",{"_35":870,"_37":3641,"_39":506,"_41":3642,"_66":3643,"_68":3644,"_70":69},"_UjppcXd",{"_273":323},[],"1. Introduction",{"_31":3646,"_33":3831},[3647,3654,3661,3670,3698,3705],{"_31":3648,"_33":3649},[],{"_35":160,"_37":3650,"_39":506,"_41":3651,"_66":3652,"_68":3653,"_70":69},"bI_pQ529",{},[],"In general, open hypermedia systems tend to implement a link service layer which provides the storage and access mechanism for links and anchors. The Dexter reference model ( Halasz & Mayer, 1994 ) refers to this as the storage layer . Some systems call this layer a hyperbase ; such systems usually store not only the links and anchors, but also the nodes in this layer. The distinctions between the different types of system are ill defined, and anyway not the subject of this paper. The thing that all such systems have in common is that the application layer (or runtime layer) is physically separate from the storage layer, and that there is some system of message passing between the two, which allows the applications (editors, viewers) to send and receive messages and query the link service concerning hypertext services.",{"_31":3655,"_33":3656},[],{"_35":160,"_37":3657,"_39":506,"_41":3658,"_66":3659,"_68":3660,"_70":69},"WEDP0XkW",{},[],"All systems designers have developed their own private protocols for communicating with the link service, and these protocols are so deeply buried into the system code that in general it would involve a major re- implementation to rewrite the system to adhere to some new, standard protocol. However, the topics of these communication are essentially similar and it should quite possible to abstract a common set of messages. We suggest that the difference between different system protocols could be resolved if each system produced a protocol shim which would sit between the application and the link service as shown in figure 1.",{"_31":3662,"_33":3663},[],{"_35":1875,"_37":3664,"_39":506,"_41":3665,"_66":3667,"_68":3668,"_70":3669},"VMfk4zsc",{"_273":323,"_2135":3666},525.3658536585366,[],"Figure 1: Protocol conversion using a protocol shim.","ipfs://bafkreie7wilfgvat6int7a4exffioyaziwghnem3zti5ua2dp7fmngrcla",{"_31":3671,"_33":3693},[3672,3679,3686],{"_31":3673,"_33":3674},[],{"_35":160,"_37":3675,"_39":506,"_41":3676,"_66":3677,"_68":3678,"_70":69},"PH5qDjwk",{},[],"Once an application (for example a word processor) had been adapted to communicate using the standard protocol (for example, using an application macro language) , then it would be possible to circulate the code extensions or macros so that any system would be able to benefit from this \"hypertext aware\" application.",{"_31":3680,"_33":3681},[],{"_35":160,"_37":3682,"_39":506,"_41":3683,"_66":3684,"_68":3685,"_70":69},"PjPH2kuR",{},[],"Each system developer need develop just one extension to their system (the protocol shim itself)",{"_31":3687,"_33":3688},[],{"_35":160,"_37":3689,"_39":506,"_41":3690,"_66":3691,"_68":3692,"_70":69},"rO1w3nIF",{},[],"Applications that have been developed specifically as hypermedia viewer/editors could be used in other systems, so long as they observed the protocols.",{"_35":160,"_37":3694,"_39":506,"_41":3695,"_66":3696,"_68":3697,"_70":69},"2pS6DT5o",{"_273":274},[],"The advantages of this scheme are:",{"_31":3699,"_33":3700},[],{"_35":160,"_37":3701,"_39":506,"_41":3702,"_66":3703,"_68":3704,"_70":69},"vskfXf0j",{},[],"The problem with this approach is that some hypermedia systems have much heavier weight requirements on their protocols than others. However many developers have recently acknowledged that it is necessary to accept the concept of \"levels of awareness\" (e.g. Davis et al., 1994 , Wiil, 1996 ), and that it will not always be possible or reasonable to expect the highest level of hypertext functionality from every third party application. Reflecting these pragmatic observations we propose that the OHP protocol will have a number of levels of conformity, and it would thus be possible to describe a given application as OHP aware to some given level.",{"_31":3706,"_33":3826},[3707,3735,3742,3770,3777,3812,3819],{"_31":3708,"_33":3730},[3709,3716,3723],{"_31":3710,"_33":3711},[],{"_35":160,"_37":3712,"_39":506,"_41":3713,"_66":3714,"_68":3715,"_70":69},"1WBVrx9G",{},[],"where anchors are stored;",{"_31":3717,"_33":3718},[],{"_35":160,"_37":3719,"_39":506,"_41":3720,"_66":3721,"_68":3722,"_70":69},"TYvRHRVQ",{},[],"how new anchors are allocated;",{"_31":3724,"_33":3725},[],{"_35":160,"_37":3726,"_39":506,"_41":3727,"_66":3728,"_68":3729,"_70":69},"naRIyZkY",{},[],"how the anchor refers to the object within the node data that is to be the physical manifestation of that anchor.",{"_35":160,"_37":3731,"_39":506,"_41":3732,"_66":3733,"_68":3734,"_70":69},"O12BrB62",{"_273":274},[],"One of the major differences between hypertext implementations is the way that anchors have been treated (Davis, 1995 ). The issues, from the point of view of hypertext enabling third party applications, are: ",{"_31":3736,"_33":3737},[],{"_35":160,"_37":3738,"_39":506,"_41":3739,"_66":3740,"_68":3741,"_70":69},"acn7i31u",{},[],"Questions about the behaviour of anchors (are anchors actually processes, and what happens when an anchor is activated?) are not of interest in this context, as they are dealt with within the link service rather than within the application. For the purposes of this discussion we will follow Leggett & Schnase's (1994 ) distinction between an anchor (a hypertext object which describes one or other end of a link) and a persistent selection (that object within the node data which is the physical manifestation of the link anchor, such as a coloured text string).",{"_31":3743,"_33":3765},[3744,3751,3758],{"_31":3745,"_33":3746},[],{"_35":160,"_37":3747,"_39":506,"_41":3748,"_66":3749,"_68":3750,"_70":69},"Y4wXR8kM",{},[],"counting: e.g. \"the string at bytes 1023-1043 through the file\", \"the 8th line of the 12th paragraph\", \"the rectangle of dimensions (45,20) pixels at co-ordinates (1427,2393) in the bitmap\", etc.;",{"_31":3752,"_33":3753},[],{"_35":160,"_37":3754,"_39":506,"_41":3755,"_66":3756,"_68":3757,"_70":69},"JRKXjupW",{},[],"naming : e.g. \"the bookmark called 'MyBookmark' \", \"the spreadsheet cell range called 'Total' \", \"the drawing object named 'GasMain4' \", \"the section of a text named 'Conclusions' \", etc.; ",{"_31":3759,"_33":3760},[],{"_35":160,"_37":3761,"_39":506,"_41":3762,"_66":3763,"_68":3764,"_70":69},"LasDSYUA",{},[],"searching: e.g. \"the first occurrence in the file of the string 'Xanadu' \", \"the record in a database that results from this SQL query\", etc.",{"_35":160,"_37":3766,"_39":506,"_41":3767,"_66":3768,"_68":3769,"_70":69},"3GaW26Df",{"_273":274},[],"Probably the most generic description of the anchor is provided by Grønbæk & Trigg (1996) , in which an anchor is described as a binding between a component identifier and a location specifier (LocSpec). A LocSpec contains the details which describe a persistent selection, and the semantics of these details are decided by the application at the time that the anchor is created and resolved using the same algorithm when the anchor is loaded again at a later time. A similar generalisation of the nature of these details comes from the HyTime standard(DeRose & Durand, 1994) which allows that anchors might reference objects within the node using:",{"_31":3771,"_33":3772},[],{"_35":160,"_37":3773,"_39":506,"_41":3774,"_66":3775,"_68":3776,"_70":69},"bWtHuJoq",{},[],"HyTime also allows that references might be made of combinations of these methods, e.g. \"The first occurrence of the string 'Xanadu' in the 5th paragraph of the chapter named 'history' \".",{"_31":3778,"_33":3807},[3779,3786,3793,3800],{"_31":3780,"_33":3781},[],{"_35":160,"_37":3782,"_39":506,"_41":3783,"_66":3784,"_68":3785,"_70":69},"UP_oMmYE",{},[],"The application embeds the anchor in the node data. In this case the application may also embed all the link information at this point (e.g. URL's embedded in html as HREF's) or might allocate an ID to the anchor which is unique to this node, and which will specify to the link service the link or links in which the anchor participates, as in Hyper-G (Andrews et al., 1995 ).",{"_31":3787,"_33":3788},[],{"_35":160,"_37":3789,"_39":506,"_41":3790,"_66":3791,"_68":3792,"_70":69},"WW7m1U94",{},[],"The application allocates an ID for the anchor, which will be unique for that node, and takes responsibility for maintaining a table of IDs and LocSpecs belonging to the node. The link service can resolve an anchor by using the (node name, anchor ID) pair. This is the approach taken by most Dexter based systems such as DHM.",{"_31":3794,"_33":3795},[],{"_35":160,"_37":3796,"_39":506,"_41":3797,"_66":3798,"_68":3799,"_70":69},"R9kZHSif",{},[],"The application requests that the link service allocates an ID for the anchor, which will be unique over the entire link service. The application will still need to maintain a table of anchor IDs and LocSpecs at run time. This approach is taken by Multicard and the hyperbase class of systems.",{"_31":3801,"_33":3802},[],{"_35":160,"_37":3803,"_39":506,"_41":3804,"_66":3805,"_68":3806,"_70":69},"vwNpP6KS",{},[],"The application talks to the linkservice by transmitting the node identifier and LocSpec, and allocates no specific anchor ID at all. This is the approach taken by Microcosm.",{"_35":160,"_37":3808,"_39":506,"_41":3809,"_66":3810,"_68":3811,"_70":69},"r5GIxFzt",{"_273":2113},[],"Different systems allocate anchors in different ways. There are four principle methods:",{"_31":3813,"_33":3814},[],{"_35":160,"_37":3815,"_39":506,"_41":3816,"_66":3817,"_68":3818,"_70":69},"6imlPA9o",{},[],"In designing our protocol, we must produce a standard which allows existing and future hypermedia systems to participate, regardless of the method they use to represent anchors or LocSpecs or the way that they allocate and store anchors.",{"_31":3820,"_33":3821},[],{"_35":160,"_37":3822,"_39":506,"_41":3823,"_66":3824,"_68":3825,"_70":69},"7cmpD3_9",{},[],"So far, the discussion of anchors has assumed that all anchors will be represented by some persistent selection or button within the node data when the data is displayed. Hypertext links are invoked by clicking on the button. This traditional interface to hypermedia is well established, but has limitations that are discussed in Hall (1994) . An alternative interface to hypermedia is the \"selection and action\" metaphor which has been pioneered in Microcosm, which enables the user to make dynamic queries of the system, for example by selecting some text string and asking the system to compute links using some dynamic information retrieval algorithm. The protocols will need to support this form of hypertext interaction.",{"_35":870,"_37":3827,"_39":506,"_41":3828,"_66":3829,"_68":3830,"_70":69},"osWSojwU",{"_273":323},[],"3. Anchors",{"_35":870,"_37":3832,"_39":506,"_41":3833,"_66":3834,"_68":3835,"_70":69},"n1MdTW1q",{"_273":323},[],"2. The Protocol Shim",{"_31":3837,"_33":3881},[3838,3859,3866,3875],{"_31":3839,"_33":3854},[3840,3847],{"_31":3841,"_33":3842},[],{"_35":160,"_37":3843,"_39":506,"_41":3844,"_66":3845,"_68":3846,"_70":69},"igGYJBUf",{},[],"applications that have been enabled for one communication protocol will only be transferable to other systems if that other system has a shim using that protocol.",{"_31":3848,"_33":3849},[],{"_35":160,"_37":3850,"_39":506,"_41":3851,"_66":3852,"_68":3853,"_70":69},"m-jFqyfg",{},[],"it would be preferable to build shims that will allow clients on one machine architecture to communicate with link services on other architectures.",{"_35":160,"_37":3855,"_39":506,"_41":3856,"_66":3857,"_68":3858,"_70":69},"Rgd9zcsr",{"_273":274},[],"The question of the choice of communication protocol is interesting. The communication is clearly peer-to-peer in the sense that either the shim or the node viewer might initiate a message. We could agree that any suitable method could be used (e.g. DDE on Windows, AppleEvents on the Mac, RPC on Unix), but this approach has problems:",{"_31":3860,"_33":3861},[],{"_35":160,"_37":3862,"_39":506,"_41":3863,"_66":3864,"_68":3865,"_70":69},"0mKnCdin",{},[],"For these reasons it makes sense to separate the choice of communication protocol from the hypertext protocol, as shown in figure 2. In this configuration, the application developer produces a communication shim to run on the client side. This shim understands the application protocol (e.g. DDE) and converts it to whatever network protocol is required (e.g. sockets). As we shall see later, this shim needs to be more than just a communication protocol converter, and is required to have some hypertext functionality. The linkservice developer produces the protocol shim, which runs on the same platform as the linkservice, and accepts incoming messages in whatever network protocols are supported.",{"_31":3867,"_33":3868},[],{"_35":1875,"_37":3869,"_39":506,"_41":3870,"_66":3872,"_68":3873,"_70":3874},"ZNdCJPEv",{"_273":323,"_2135":3871},624.6575342465753,[],"Figure 2: Communication Protocol Conversion","ipfs://bafkreig5skrxskds2pd7ez3kdlzf3lgu4fljqtubp4nyfn5ehcnqutoj4u",{"_31":3876,"_33":3877},[],{"_35":160,"_37":3878,"_39":506,"_41":3879,"_66":3880,"_68":69,"_70":69},"ciz4GBsD",{},[],{"_35":870,"_37":3882,"_39":506,"_41":3883,"_66":3884,"_68":3885,"_70":69},"Gs23YdHO",{"_273":323},[],"4. Communication Protocols",{"_31":3887,"_33":4625},[3888,3966,4005,4031,4052,4093,4331,4471,4562],{"_31":3889,"_33":3961},[3890,3897,3905,3912,3933,3940,3947,3954],{"_31":3891,"_33":3892},[],{"_35":160,"_37":3893,"_39":506,"_41":3894,"_66":3895,"_68":3896,"_70":69},"MhFcdrdm",{},[],"The difficulty in defining a standard LocSpec is that if it is to be sufficiently flexible to meet all possible ways of expressing positions in a document as intended by the HyTime standard (see section 3 ) then it will be difficult to parse and thus put considerable onus on the application. Instead we suggest the following simplification, at least for the purpose of getting the standard started. We expect that it will evolve.",{"_31":3898,"_33":3899},[],{"_35":2026,"_37":3900,"_39":506,"_41":3901,"_66":3903,"_68":3904,"_70":69},"zJkRNj-o",{"_2029":3902},"xml",[],"LocSpec ::=\n\n{\\ContentType MimeType\n\\Content Mime encoded text string\n\\Count [Comma separated list of numbers]\n\\ReverseCount [Comma separated list of numbers]\n\\Name [Mime encoded text string]\n\\Script [Viewer Executable Script] }\n ",{"_31":3906,"_33":3907},[],{"_35":160,"_37":3908,"_39":506,"_41":3909,"_66":3910,"_68":3911,"_70":69},"Ms5IYXrX",{},[],"The important thing to realise about the LocSpec is that although the link service may be required to store this information, it is not usually required to interpret the information in any way. The semantics of the various fields within the LocSpec are decided by the viewer at the time that it creates the LocSpec, and then stored in the linkservice for later retrieval and interpretation by the same viewer. Thus different viewers are not required to keep to any particular convention for representing these fields.",{"_31":3913,"_33":3928},[3914,3921],{"_31":3915,"_33":3916},[],{"_35":160,"_37":3917,"_39":506,"_41":3918,"_66":3919,"_68":3920,"_70":69},"m67jubb7",{},[],"some link services may attempt to search their databases for anchors that have particular attributes;",{"_31":3922,"_33":3923},[],{"_35":160,"_37":3924,"_39":506,"_41":3925,"_66":3926,"_68":3927,"_70":69},"hm-SmDx3",{},[],"extra information is generally useful if it becomes necessary to mend the position of the anchor after a document has been edited by an editor that was not linkservice aware.",{"_35":160,"_37":3929,"_39":506,"_41":3930,"_66":3931,"_68":3932,"_70":69},"2yOxsHZD",{"_273":274},[],"The one exception to the above rule is the content. Some hypermedia systems store the content of the anchors within the linkservice, and use this information as the basis for providing services. For example, Microcosm searches its linkbases for links authored on particular content in order to provide generic links. For this reason, this part of the LocSpec is not optional. The protocol requires that the LocSpec contains at least one method for the viewer to store information about the position of an anchor. However, it is strongly recommended that application developers try to fill as many of these fields as possible. The reasons for this recommendation are that:",{"_31":3934,"_33":3935},[],{"_35":160,"_37":3936,"_39":506,"_41":3937,"_66":3938,"_68":3939,"_70":69},"U_6kbSEW",{},[],"The comma separated list of numbers used in the count and reverse count will depend on the method used by the viewer to represent positions in documents, e.g. 3, 2, 5, 423 might be used by a structured document to mean the 423rd character in the 5th paragraph of section 3.2. Alternatively it might represent the top left and bottom right co-ordinates of a rectangle in a bitmap.",{"_31":3941,"_33":3942},[],{"_35":160,"_37":3943,"_39":506,"_41":3944,"_66":3945,"_68":3946,"_70":69},"GHq3B9z3",{},[],"The reverse offset allows us to represent a position by counting from the end of a document. This overloading can be useful when trying to fix LocSpecs that have become broken due to document editing.",{"_31":3948,"_33":3949},[],{"_35":160,"_37":3950,"_39":506,"_41":3951,"_66":3952,"_68":3953,"_70":69},"xLkOk4gF",{},[],"The name may be any object understood by the viewer which is unique to the current document, such as a bookmark name or a drawing object.",{"_31":3955,"_33":3956},[],{"_35":160,"_37":3957,"_39":506,"_41":3958,"_66":3959,"_68":3960,"_70":69},"XtIptj86",{},[],"The script is a set of instructions which may be interpreted by the application which will enable the application to locate the object.",{"_35":870,"_37":3962,"_39":506,"_41":3963,"_66":3964,"_68":3965,"_70":69},"mOnD-Xu5",{"_273":323},[],"5.1. LocSpecs",{"_31":3967,"_33":4000},[3968,3974,3980,3986,3993],{"_31":3969,"_33":3970},[],{"_35":160,"_37":3971,"_39":506,"_41":3972,"_66":3973,"_68":3075,"_70":69},"KmtbRkMQ",{},[],{"_31":3975,"_33":3976},[],{"_35":160,"_37":3977,"_39":506,"_41":3978,"_66":3979,"_68":3082,"_70":69},"JvMRUab6",{},[],{"_31":3981,"_33":3982},[],{"_35":160,"_37":3983,"_39":506,"_41":3984,"_66":3985,"_68":3089,"_70":69},"0NLnE6Wy",{},[],{"_31":3987,"_33":3988},[],{"_35":160,"_37":3989,"_39":506,"_41":3990,"_66":3991,"_68":3992,"_70":69},"o-PSQogi",{},[],"For the purpose of this version of the protocol we suggest that the information about presentation is kept viewer specific. i.e. the viewer may ask to store any presentation information in any form that it chooses, and the viewer will interpret this data at a later stage when asked to present the data again.",{"_31":3994,"_33":3995},[],{"_35":160,"_37":3996,"_39":506,"_41":3997,"_66":3998,"_68":3999,"_70":69},"Qk5A7YuX",{},[],"The consequence of this policy will be that link services will not be able to communicate to the viewer that it should change any presentation (e.g. as the result of a script) since it will not know the syntax of the presentation tag for this particular viewer. Later versions of the protocol should standardise the form of this information, e.g. by defining the data as {colour, style, visibility} and giving a set of values and meanings to each of these parameters.",{"_35":870,"_37":4001,"_39":506,"_41":4002,"_66":4003,"_68":4004,"_70":69},"TKS_BzEx",{"_273":323},[],"5.2. Presentation Specifics",{"_31":4006,"_33":4026},[4007],{"_31":4008,"_33":4022},[4009,4015],{"_31":4010,"_33":4011},[],{"_35":160,"_37":4012,"_39":506,"_41":4013,"_66":4014,"_68":2712,"_70":69},"3HJpfcxs",{},[],{"_31":4016,"_33":4017},[],{"_35":160,"_37":4018,"_39":506,"_41":4019,"_66":4020,"_68":4021,"_70":69},"jTCmKGlg",{},[],"Client End Scripts. These are scripts that are sent to the viewer by the linkserver. In general they are either sent as part of a LocSpec in order to identify an anchor, or they are sent as a process which the viewer will be expected to run, for example in order to change the presentation of the data in some way. OHP must provide support for such scripts if the viewer wishes to use them. ",{"_35":160,"_37":4023,"_39":506,"_41":4024,"_66":4025,"_68":2724,"_70":69},"8RAgD94T",{"_273":323},[],{"_35":870,"_37":4027,"_39":506,"_41":4028,"_66":4029,"_68":4030,"_70":69},"_uYKnJWf",{"_273":323},[],"5.3. Scripts",{"_31":4032,"_33":4047},[4033,4040],{"_31":4034,"_33":4035},[],{"_35":160,"_37":4036,"_39":506,"_41":4037,"_66":4038,"_68":4039,"_70":69},"MuNu-AVQ",{},[],"It is quite possible that one communication shim may need to maintain communication with more than one application on a client machine, and also quite possible that one application might be concurrently displaying more than one node (e.g. an MDI application in Windows). Similarly, one link server (and protocol shim) may need to maintain communication with more than one client. For this reason it is necessary that messages contain routing information, so that messages sent by the link service are sent to the correct node in the correct application on the correct machine. However, from the point of view of the application developer, it is not necessary to know anything about the content of the routing information. The link service will provide the information to the application, and the application will be responsible for returning this information every time it sends a message to the link service, so that the link service can identify where to reply. This information is known in the protocol as the Channel .",{"_31":4041,"_33":4042},[],{"_35":160,"_37":4043,"_39":506,"_41":4044,"_66":4045,"_68":4046,"_70":69},"55XUfsbA",{},[],"Since the linkservice will maintain a unique channel to each document that is currently connected, it will not be necessary for most of the messages to pass the document name, as this is implicit in the channel. However, there would be nothing to prevent the linkservice explicitly using the document name as part of the channel information.",{"_35":870,"_37":4048,"_39":506,"_41":4049,"_66":4050,"_68":4051,"_70":69},"p8tpaWdv",{"_273":323},[],"5.4. Communication Channels",{"_31":4053,"_33":4088},[4054,4061,4068,4075,4082],{"_31":4055,"_33":4056},[],{"_35":160,"_37":4057,"_39":506,"_41":4058,"_66":4059,"_68":4060,"_70":69},"WcUI1pko",{},[],"OHP is a peer to peer asynchronous protocol. Messages may be sent by either the link service or by the editor / viewer, and no message waits for any form of reply. If a reply is expected, it is up to the receiving component to initiate a new message. There are thus two classes of message to be considered; those sent by the viewer and those sent by the link service.",{"_31":4062,"_33":4063},[],{"_35":160,"_37":4064,"_39":506,"_41":4065,"_66":4066,"_68":4067,"_70":69},"EV57sWC3",{},[],"Messages that the viewer may send will depend largely on the set of services that can be handled by the link server. It therefore makes sense that part of the protocol will allow the definition of the subjects which the link server can handle. These subjects do not need to be known in advance.",{"_31":4069,"_33":4070},[],{"_35":160,"_37":4071,"_39":506,"_41":4072,"_66":4073,"_68":4074,"_70":69},"fSKK4DWB",{},[],"On the other hand, the messages which the link server may send to the viewer must be defined in advance, since the viewer must be coded to deal with these messages.",{"_31":4076,"_33":4077},[],{"_35":160,"_37":4078,"_39":506,"_41":4079,"_66":4080,"_68":4081,"_70":69},"Zz7RObr4",{},[],"OHP messages will consist of text strings. In the following sections the messages are shown formatted on multiple lines for ease of presentation. However, the messages themselves will be one continuous stream of ASCII text, unbroken by line breaks. The messages consist of Tags, which are proceeded by a backslash ('') and succeeded by a space. The characters that follow, up to the next tag or the end of the message are the tag contents. A tag content may be empty if shown as optional in the message definition. The tags of each message are all compulsory, and must be presented in the order in the message definition. If a backslash ('') or closing curly bracket ('{' or '}') occurs within the tag content, then it should be quoted by preceding it with a further backslash. The bold '+ ' is used in the following descriptions to indicate that one or more of the line indicated may be included at this point.",{"_31":4083,"_33":4084},[],{"_35":160,"_37":4085,"_39":506,"_41":4086,"_66":4087,"_68":1994,"_70":69},"SSq8FTJ_",{},[],{"_35":870,"_37":4089,"_39":506,"_41":4090,"_66":4091,"_68":4092,"_70":69},"XRGeIQRc",{"_273":323},[],"5.5. Form of the Protocol",{"_31":4094,"_33":4326},[4095,4130,4179,4200,4242],{"_31":4096,"_33":4125},[4097,4104,4111,4118],{"_31":4098,"_33":4099},[],{"_35":2026,"_37":4100,"_39":506,"_41":4101,"_66":4102,"_68":4103,"_70":69},"06SjGCJM",{"_2029":69},[],"\n\\Subject HeresServices\n\\Data {\\Menuitem Menuitem \\Service Service } +\n\\Channel Channel\n",{"_31":4105,"_33":4106},[],{"_35":160,"_37":4107,"_39":506,"_41":4108,"_66":4109,"_68":4110,"_70":69},"W-ygxpZU",{},[],"Which will define the menu that will be placed on the viewer, and the set of services that will be requested from the link service when such items are selected from the menu.",{"_31":4112,"_33":4113},[],{"_35":160,"_37":4114,"_39":506,"_41":4115,"_66":4116,"_68":4117,"_70":69},"aNZXyDz6",{},[],"For example, a Microcosm link server would typically send the following: ",{"_31":4119,"_33":4120},[],{"_35":2026,"_37":4121,"_39":506,"_41":4122,"_66":4123,"_68":4124,"_70":69},"h9oZNk0z",{"_2029":69},[],"\\Subject HeresServices\n\\Data {\\Menuitem Follow Link\\Service FOLLOW.LINK}\n\\Data {\\Menuitem Show Links\\Service SHOW.LINKS}\n\\Data {\\Menuitem Compute Links\\Service COMPUTE.LINKS} \\Data {\\Menuitem Make Start Anchor\\Service START.LINK} \\Data {\\Menuitem Make End Anchor\\Service END.LINK} \\Channel #9",{"_35":870,"_37":4126,"_39":506,"_41":4127,"_66":4128,"_68":4129,"_70":69},"KHiKyeZ6",{"_273":323},[],"5.6.1. HeresServices",{"_31":4131,"_33":4174},[4132,4139,4146,4153,4160,4167],{"_31":4133,"_33":4134},[],{"_35":2026,"_37":4135,"_39":506,"_41":4136,"_66":4137,"_68":4138,"_70":69},"7zZN_fhH",{"_2029":69},[],"\n\\Subject LaunchDocument\n\\DocumentName DocName\n\\ReadOnly True/False\n\\DocumentNickName [DocNickName]\n\\DocumentType MimeType\n\\DataCallBack True or False \n\\Channel Channel\n",{"_31":4140,"_33":4141},[],{"_35":160,"_37":4142,"_39":506,"_41":4143,"_66":4144,"_68":4145,"_70":69},"qHmj4ee6",{},[],"This message introduces a special problem. At the time that it is sent there may be no viewer open to receive the message! The linkserver has requested that a particular document of a particular type is opened, but at present the viewer for this data type is not running. It is necessary that there is some component at the client end to receive this message that can arrange to fire up the appropriate viewer. We suggest that this functionality should be added to the communication protocol shim, which is anyway at the client end. The shim will need to know which viewer to load, depending upon the mime type of the data. The viewer, when it has been launched will receive this message will be responsible for storing the channel information and using it whenever sending messages back to the linkservice.",{"_31":4147,"_33":4148},[],{"_35":160,"_37":4149,"_39":506,"_41":4150,"_66":4151,"_68":4152,"_70":69},"retaYn4-",{},[],"A further problem is introduced by the fact that some systems would expect the client viewer to now arrange to fetch its own data (using the document name to describe a file on the file system or a remote server) whereas other systems might expect that the data will be held within the linkservice (hyperbase). The DataCallback tag, allows the linkservice to indicate that it wishes the viewer to send a message back asking for the data, and if such a call-back occurs it will answer with a HeresDocument message. If the call-back is false the linkservice will expect the viewer to arrange to load its own data.",{"_31":4154,"_33":4155},[],{"_35":160,"_37":4156,"_39":506,"_41":4157,"_66":4158,"_68":4159,"_70":69},"W-6FQEY5",{},[],"It is also a useful point to introduce the idea of levels of the protocol. Many linkservices allow third party applications to participate in the hypertext, in so far as they may be launched and run with given node data, and they may be closed. This is the functionality that is supported by OHP Level 0. In this case the will be expected to handle messages to open the node (LaunchDocument) and close the node (CloseNode). The application itself is not expected to deliver and hypermedia functionality. All other messages in this document are part of the Level 1 Protocol. Level 2 of the protocol is not yet defined, but is discussed in the section 8. The client end communication shim is responsible for knowing the level of the applications it launches so that it does not attempt to send messages to non-communicating applications, but instead returns error messages. In this respect the shim acts as a proxy for the application. ",{"_31":4161,"_33":4162},[],{"_35":160,"_37":4163,"_39":506,"_41":4164,"_66":4165,"_68":4166,"_70":69},"spYDV0Y7",{},[],"The ReadOnly Tag enables the link service to inform the viewer that it should not allow the user to edit the node contents.",{"_31":4168,"_33":4169},[],{"_35":160,"_37":4170,"_39":506,"_41":4171,"_66":4172,"_68":4173,"_70":69},"v50biUWJ",{},[],"The DocumentNickName allows for the case where the linkservice may supply better descriptions of the document than the filename alone, and the viewer may elect to display this name somewhere, typically in the title bar.",{"_35":870,"_37":4175,"_39":506,"_41":4176,"_66":4177,"_68":4178,"_70":69},"zncBOWBp",{"_273":323},[],"5.6.2. LaunchDocument",{"_31":4180,"_33":4195},[4181,4188],{"_31":4182,"_33":4183},[],{"_35":160,"_37":4184,"_39":506,"_41":4185,"_66":4186,"_68":4187,"_70":69},"ZkircEXT",{},[],"This message is sent by the linkservice if it has received a call-back asking the linkservice to supply the document data.",{"_31":4189,"_33":4190},[],{"_35":2026,"_37":4191,"_39":506,"_41":4192,"_66":4193,"_68":4194,"_70":69},"z142Hszk",{"_2029":69},[],"\\Subject HeresDocument\n\\Data Mime Encoded Data\n\\Channel Channel ",{"_35":870,"_37":4196,"_39":506,"_41":4197,"_66":4198,"_68":4199,"_70":69},"XGl5aFjv",{"_273":323},[],"5.6.3. HeresDocument",{"_31":4201,"_33":4237},[4202,4209,4216,4223,4230],{"_31":4203,"_33":4204},[],{"_35":160,"_37":4205,"_39":506,"_41":4206,"_66":4207,"_68":4208,"_70":69},"J_8sYEBl",{},[],"After a document is launched the viewer may request the anchor table. This linkservice will reply with this message.",{"_31":4210,"_33":4211},[],{"_35":2026,"_37":4212,"_39":506,"_41":4213,"_66":4214,"_68":4215,"_70":69},"2tLbu5RZ",{"_2029":69},[],"\\Subject HeresAnchorTable\n\\Data {\\AnchorID AnchorID\n \\LocSpec LocSpec\n \\Direction Start/End/Bidirect\n \\Presentation colour,style,display\n \\Service Service } +\n\\Channel Channel",{"_31":4217,"_33":4218},[],{"_35":160,"_37":4219,"_39":506,"_41":4220,"_66":4221,"_68":4222,"_70":69},"STECK3k8",{},[],"An anchor record is thus seen to consist of an unique identifier, a LocSpec, a direction and a service.",{"_31":4224,"_33":4225},[],{"_35":160,"_37":4226,"_39":506,"_41":4227,"_66":4228,"_68":4229,"_70":69},"siF0U7xs",{},[],"The direction field allows the linkservice to specify whether the given anchor is the start of a link, the end of alink, or one end of a bi-directional link.",{"_31":4231,"_33":4232},[],{"_35":160,"_37":4233,"_39":506,"_41":4234,"_66":4235,"_68":4236,"_70":69},"W7AlcnQY",{},[],"The service field allows for the case that not all hypertext buttons will require a Follow Link type of service. Sometimes a anchor may be created that causes some other service (e.g. dynamically generate links) to be requested.",{"_35":870,"_37":4238,"_39":506,"_41":4239,"_66":4240,"_68":4241,"_70":69},"ADD9M4xt",{"_273":323},[],"5.6.4. HeresAnchorTable",{"_31":4243,"_33":4321},[4244,4251,4265,4279,4293,4307],{"_31":4245,"_33":4246},[],{"_35":160,"_37":4247,"_39":506,"_41":4248,"_66":4249,"_68":4250,"_70":69},"_du9I3d2",{},[],"When a document is launched, or possibly at some other time, it will often be necessary to send a message requesting that a particular anchor is displayed, e.g. by moving the cursor to the anchor, or highlighting the anchor. This message is sent to the viewer to request such an action. \\Subject DisplayAnchor \\AnchorID AnchorID \\Presentation colour,style,display \\Channel Channel",{"_31":4252,"_33":4260},[4253],{"_31":4254,"_33":4255},[],{"_35":160,"_37":4256,"_39":506,"_41":4257,"_66":4258,"_68":4259,"_70":69},"JJ7BgY6e",{},[],"Sometimes it is necessary to display something other than a pre-defined anchor, for example, the result of a search. This message may define the object to be viewed. \\Subject DisplayLocSpec \\LocSpec LocSpec \\Presentation colour,style,display \\Channel Channel",{"_35":870,"_37":4261,"_39":506,"_41":4262,"_66":4263,"_68":4264,"_70":69},"3py1gF1X",{"_273":323},[],"5.6.6. DisplayLocSpec",{"_31":4266,"_33":4274},[4267],{"_31":4268,"_33":4269},[],{"_35":160,"_37":4270,"_39":506,"_41":4271,"_66":4272,"_68":4273,"_70":69},"Gi7hsa8x",{},[],"The protocol requires that the viewer is not responsible for allocating anchor ID's. Instead a message will be sent to the linkservice asking for an anchor ID, and the linkservice will reply: \\Subject HeresNewAnchor \\Data {\\AnchorID AnchorID \\LocSpec LocSpec \\Direction Start/End/Bidirect \\Presentation colour,style,display \\Service Service } \\Channel Channel ",{"_35":870,"_37":4275,"_39":506,"_41":4276,"_66":4277,"_68":4278,"_70":69},"C_IAGFpR",{"_273":323},[],"5.6.7. HeresNewAnchor",{"_31":4280,"_33":4288},[4281],{"_31":4282,"_33":4283},[],{"_35":160,"_37":4284,"_39":506,"_41":4285,"_66":4286,"_68":4287,"_70":69},"i1xY2JMn",{},[],"This message allows the link service to send scripts to the application which the application will interpret. Such scripts might alter the presentation of a node, change the contents of a node or anything else that the interpreter contained in the application is capable of undertaking. \\Subject Interpret \\ScriptType ScriptingLanguage \\Data { Script } \\Channel Channel The ScriptType tag will define the interpreter that will be required by the application that receives the following script. In the simplest case an application might interpret keystrokes that could be played to the application. At the other end of the scale, the application might implement a Java interpreter. The protocol may need extra messages to allow the linkservice to query the application to discover the scripting language(s) that it can handle. In its current form the linkservice must either know what languages can be handled, or must accept that the script may be ignored. ",{"_35":870,"_37":4289,"_39":506,"_41":4290,"_66":4291,"_68":4292,"_70":69},"PMhSUQtn",{"_273":323},[],"5.6.8. Interpret",{"_31":4294,"_33":4302},[4295],{"_31":4296,"_33":4297},[],{"_35":160,"_37":4298,"_39":506,"_41":4299,"_66":4300,"_68":4301,"_70":69},"c64sTS85",{},[],"This message is sent by the linkservice to an application when it has requested a new connection to the linkservice (see CreateNode below). \\Subject HeresNewChannel \\SendDocument True / False \\DocumentNickName [DocNickName] \\Channel Channel The SendDocument Tag is used by the linkservice to request that the viewer follows up by actually sending the contents of the node, as is required by many of the hyperbase variety of linkservices. If the linkservice already knows of the document, and has a nickname for the document, it will return this.",{"_35":870,"_37":4303,"_39":506,"_41":4304,"_66":4305,"_68":4306,"_70":69},"L0Ef6hTs",{"_273":323},[],"5.6.9. HeresNewChannel",{"_31":4308,"_33":4316},[4309],{"_31":4310,"_33":4311},[],{"_35":160,"_37":4312,"_39":496,"_41":4313,"_66":4314,"_68":4315,"_70":69},"m0NLDUeZ",{},[],"This message is sent by the link service to a node that it wishes to automatically close. \\Subject CloseNode \\UpdateNode True / False \\Channel Channel The application is then responsible for closing itself, ensuring that it has updated any anchors and its contents if required by the UpdateNode tag. ",{"_35":870,"_37":4317,"_39":496,"_41":4318,"_66":4319,"_68":4320,"_70":69},"ZnAgugjk",{"_273":323},[],"5.6.10. CloseNode",{"_35":870,"_37":4322,"_39":506,"_41":4323,"_66":4324,"_68":4325,"_70":69},"zfqdoPlR",{"_273":323},[],"5.6.5. DisplayAnchor",{"_35":870,"_37":4327,"_39":506,"_41":4328,"_66":4329,"_68":4330,"_70":69},"Ry4wX0yo",{"_273":323},[],"5.6. Messages that the linkserver may send",{"_31":4332,"_33":4466},[4333,4347,4361,4375,4410,4424,4438,4452],{"_31":4334,"_33":4342},[4335],{"_31":4336,"_33":4337},[],{"_35":160,"_37":4338,"_39":496,"_41":4339,"_66":4340,"_68":4341,"_70":69},"R0XJIehS",{},[],"This message allows the viewer to ask the linkservice to send it the contents of a node. This is only required where the linkservice actually stores the node data, and would typically be sent in response to a LaunchDocument message which had the DataCallBack flag set. The linkservice will respond with a HeresDocument message. \\Subject GetNode \\DocumentName DocName \\Channel Channel The DocumentName is redundant when calling back for a node, as the linkservice already knows this. However, this message might also be sent to request a new document.",{"_35":870,"_37":4343,"_39":496,"_41":4344,"_66":4345,"_68":4346,"_70":69},"109al9Yi",{"_273":323},[],"5.7.1. GetNode",{"_31":4348,"_33":4356},[4349],{"_31":4350,"_33":4351},[],{"_35":160,"_37":4352,"_39":496,"_41":4353,"_66":4354,"_68":4355,"_70":69},"LfEHRIJD",{},[],"When a viewer has loaded up, it will be necessary for it to ask the linkservice to itemise the set of services it may provide on a menu. \\Subject GetServices \\Channel Channel The linkservice should respond with a HeresServices message.",{"_35":870,"_37":4357,"_39":496,"_41":4358,"_66":4359,"_68":4360,"_70":69},"IEkVfLhi",{"_273":323},[],"5.7.2. GetServices",{"_31":4362,"_33":4370},[4363],{"_31":4364,"_33":4365},[],{"_35":160,"_37":4366,"_39":496,"_41":4367,"_66":4368,"_68":4369,"_70":69},"QpHc6Bpd",{},[],"The viewer, while running is expected to maintain the anchor table. It is expected to obtain the anchors from the linkservice by sending the message: \\Subject GetAnchorTable \\Channel Channel and the linkservice is expected to respond with a HeresAnchorTable message.",{"_35":870,"_37":4371,"_39":496,"_41":4372,"_66":4373,"_68":4374,"_70":69},"CfeiF5fa",{"_273":323},[],"5.7.3. GetAnchorTable",{"_31":4376,"_33":4405},[4377,4384,4391,4398],{"_31":4378,"_33":4379},[],{"_35":160,"_37":4380,"_39":496,"_41":4381,"_66":4382,"_68":4383,"_70":69},"SbJ5qg_C",{},[],"Most of the hypertext functionality will be obtained by either clicking on buttons or sensitive areas (which are representations of anchors) or making a selection and requesting an action from the menu, or simply choosing an action from the menu. In the case where a button is clicked, the viewer will know the service that is required from the anchor table. In the case where an action is chosen from the menu, this will define the required service. Messages requesting services will take the form: \\Subject RequestService \\Service Service",{"_31":4385,"_33":4386},[],{"_35":160,"_37":4387,"_39":496,"_41":4388,"_66":4389,"_68":4390,"_70":69},"PUafF6qE",{},[],"\\AnchorID [ AnchorID ] \\LocSpec [ LocSpec ] \\Presentation [ colour,style,display ] \\Channel Channel",{"_31":4392,"_33":4393},[],{"_35":160,"_37":4394,"_39":496,"_41":4395,"_66":4396,"_68":4397,"_70":69},"MF3ro--L",{},[],"The anchor ID will be empty in many of these messages, for example, when requesting that an anchor is created on a given LocSpec.",{"_31":4399,"_33":4400},[],{"_35":160,"_37":4401,"_39":496,"_41":4402,"_66":4403,"_68":4404,"_70":69},"lFITSbAY",{},[],"The LocSpec may be empty, for example in the case where a simple action has been chosen from a menu.",{"_35":870,"_37":4406,"_39":496,"_41":4407,"_66":4408,"_68":4409,"_70":69},"mxmgzq70",{"_273":323},[],"5.7.4. RequestService",{"_31":4411,"_33":4419},[4412],{"_31":4413,"_33":4414},[],{"_35":160,"_37":4415,"_39":496,"_41":4416,"_66":4417,"_68":4418,"_70":69},"eUpPCyQh",{},[],"When a document has been edited the viewer is responsible for ensuring that the LocSpecs in the anchor table are changed. Consequently it will be necessary to communicate these changes to the link service. \\Subject UpdateAnchors \\Data {\\AnchorID AnchorID \\LocSpec LocSpec \\Direction Start/End/Bidirect \\Presentation colour,style,display \\Service Service }+ \\Channel Channel",{"_35":870,"_37":4420,"_39":496,"_41":4421,"_66":4422,"_68":4423,"_70":69},"QEz5yhZF",{"_273":323},[],"5.7.5. Update Anchors",{"_31":4425,"_33":4433},[4426],{"_31":4427,"_33":4428},[],{"_35":160,"_37":4429,"_39":496,"_41":4430,"_66":4431,"_68":4432,"_70":69},"KT6szgsm",{},[],"A user may wish to register a new document that they are currently viewing with the link service. In this case there will not yet be an established channel between the document and the linkserver. The viewer/editor will send the following message. \\Subject CreateNode \\DocumentName DocName \\DocumentType MimeType When the linkservice gets the message, it will send a HeresNewChannel message back (see above), and if necessary (SendDocument = True) the viewer will then arrange to send the actual contents of the document using the UpdateNode message. Note that it is quite possible that the document concerned may already be registered with the link service: in this case this message serves only to open a communication channel to the linkserver. Also note that the message contains no information about document ownership or permissions: it is assumed that the linkservice, on receiving this message, will enter into a dialogue with the user to obtain such information.",{"_35":870,"_37":4434,"_39":496,"_41":4435,"_66":4436,"_68":4437,"_70":69},"oc4YU3xK",{"_273":323},[],"5.7.6. CreateNode",{"_31":4439,"_33":4447},[4440],{"_31":4441,"_33":4442},[],{"_35":160,"_37":4443,"_39":496,"_41":4444,"_66":4445,"_68":4446,"_70":69},"9mTY-WID",{},[],"If the contents of a node have changed during a session (or if it is a new node) it may be necessary to send the contents back to the linkservice, if the linkservice is of the type that stores the actual contents. \\Subject UpdateNode \\DocumentType MimeType \\Data Mime Encoded Data \\Channel Channel",{"_35":870,"_37":4448,"_39":496,"_41":4449,"_66":4450,"_68":4451,"_70":69},"f49YqRdm",{"_273":323},[],"5.7.7. UpdateNode",{"_31":4453,"_33":4461},[4454],{"_31":4455,"_33":4456},[],{"_35":160,"_37":4457,"_39":506,"_41":4458,"_66":4459,"_68":4460,"_70":69},"-O36dxnz",{},[],"This message is sent when a node is closed by the user. \\Subject Closing \\Channel Channel This will close the channel which may now be re-assigned.",{"_35":870,"_37":4462,"_39":496,"_41":4463,"_66":4464,"_68":4465,"_70":69},"ZR7THb4A",{"_273":323},[],"5.7.8. Closing",{"_35":870,"_37":4467,"_39":496,"_41":4468,"_66":4469,"_68":4470,"_70":69},"slM-4RfY",{"_273":323},[],"5.7. Messages that the Editor/Viewer May Send",{"_31":4472,"_33":4557},[4473,4529],{"_31":4474,"_33":4524},[4475,4482,4489,4496,4503,4510,4517],{"_31":4476,"_33":4477},[],{"_35":160,"_37":4478,"_39":496,"_41":4479,"_66":4480,"_68":4481,"_70":69},"TZ-Fdqgf",{},[],"We are very much aware that at times such protocols are insufficient for the needs of a particular problem. We therefore suggest that for experimental purposes, the following extensions to the protocol are allowed. Any message may include a tag ",{"_31":4483,"_33":4484},[],{"_35":2026,"_37":4485,"_39":496,"_41":4486,"_66":4487,"_68":4488,"_70":69},"nHuWa1ah",{"_2029":69},[],"\\Other Data",{"_31":4490,"_33":4491},[],{"_35":160,"_37":4492,"_39":496,"_41":4493,"_66":4494,"_68":4495,"_70":69},"ZAf3PK8q",{},[],"where the data may be anything that the application and the link service wish to include.",{"_31":4497,"_33":4498},[],{"_35":160,"_37":4499,"_39":496,"_41":4500,"_66":4501,"_68":4502,"_70":69},"XE7JSWaQ",{},[],"Furthermore, either the application or the linkservice may send a message",{"_31":4504,"_33":4505},[],{"_35":2026,"_37":4506,"_39":496,"_41":4507,"_66":4508,"_68":4509,"_70":69},"hUy5oW_M",{"_2029":69},[],"\\Subject Other\n\\UserDefinedTag User Defined Data +\n\\Channel Channel ",{"_31":4511,"_33":4512},[],{"_35":160,"_37":4513,"_39":496,"_41":4514,"_66":4515,"_68":4516,"_70":69},"X14zbR92",{},[],"so that they can create their own messages with their own data.",{"_31":4518,"_33":4519},[],{"_35":160,"_37":4520,"_39":496,"_41":4521,"_66":4522,"_68":4523,"_70":69},"0lVeG9WT",{},[],"Application developers are strongly encouraged to attempt to make the interpretation of these tags and messages optional at the client end, or the applications that they hypertext enable will not be transferable to other systems.",{"_35":870,"_37":4525,"_39":496,"_41":4526,"_66":4527,"_68":4528,"_70":69},"a2hd35XQ",{"_273":323},[],"5.8.1. Other",{"_31":4530,"_33":4552},[4531,4538,4545],{"_31":4532,"_33":4533},[],{"_35":160,"_37":4534,"_39":496,"_41":4535,"_66":4536,"_68":4537,"_70":69},"swum4kTT",{},[],"There may be times when a message is sent by one component that the other component does not understand or is for some reason unable to service. In these cases it may be important that the sending component is informed of the error. Either the linkservice or the editor should send an error message when it receives a message that it is unable to process.",{"_31":4539,"_33":4540},[],{"_35":2026,"_37":4541,"_39":496,"_41":4542,"_66":4543,"_68":4544,"_70":69},"IJ9GcM8N",{"_2029":69},[],"\\Subject Error \\ErrorSubject Subject tag of error message \\ErrorMessage Message \\Channel Channel",{"_31":4546,"_33":4547},[],{"_35":160,"_37":4548,"_39":496,"_41":4549,"_66":4550,"_68":4551,"_70":69},"6p38daOt",{},[],"The Error Message might be used to display in a message box to the user.",{"_35":870,"_37":4553,"_39":496,"_41":4554,"_66":4555,"_68":4556,"_70":69},"amCsHCFG",{"_273":323},[],"5.8.2. Error",{"_35":870,"_37":4558,"_39":496,"_41":4559,"_66":4560,"_68":4561,"_70":69},"NVG2D3uZ",{"_273":323},[],"5.8. Messages that both may send",{"_31":4563,"_33":4620},[4564],{"_31":4565,"_33":4615},[4566,4573,4580,4587,4594,4601,4608],{"_31":4567,"_33":4568},[],{"_35":160,"_37":4569,"_39":496,"_41":4570,"_66":4571,"_68":4572,"_70":69},"79VGxIaD",{},[],"Linkservice Requests: messages that the linkserver sends to the client asking for some action.",{"_31":4574,"_33":4575},[],{"_35":160,"_37":4576,"_39":496,"_41":4577,"_66":4578,"_68":4579,"_70":69},"pHKLkNIw",{},[],"Linkservice Replies: messages that the linkserver sends in response to all client requests.",{"_31":4581,"_33":4582},[],{"_35":160,"_37":4583,"_39":496,"_41":4584,"_66":4585,"_68":4586,"_70":69},"FabYs-W1",{},[],"Client Initialisation Requests: Messages that the client sends, typically at start-up, in order to initialise itself with the necessary linkservice information.",{"_31":4588,"_33":4589},[],{"_35":160,"_37":4590,"_39":496,"_41":4591,"_66":4592,"_68":4593,"_70":69},"7dW8M3uN",{},[],"Client Update Requests: Messages that the client sends to the linkserver to inform the linkserver of changes to the linkservice information that have occurred at the client end.",{"_31":4595,"_33":4596},[],{"_35":160,"_37":4597,"_39":496,"_41":4598,"_66":4599,"_68":4600,"_70":69},"C0YNtjVy",{},[],"Client Event Requests: Messages that are sent when a sensitive area is clicked on, or a choice has been made from a link service supplied menu. ",{"_31":4602,"_33":4603},[],{"_35":160,"_37":4604,"_39":496,"_41":4605,"_66":4606,"_68":4607,"_70":69},"zpAVANjY",{},[],"Client Replies: Messages that are sent by the client in response to requests from the linkservice.",{"_31":4609,"_33":4610},[],{"_35":160,"_37":4611,"_39":496,"_41":4612,"_66":4613,"_68":4614,"_70":69},"TYKLt_dz",{},[],"Bi-directional Messages: Messages that may be sent either way.",{"_35":160,"_37":4616,"_39":496,"_41":4617,"_66":4618,"_68":4619,"_70":69},"42ATSr4a",{"_273":274},[],"Now that we have introduced the entire protocol, it may be convenient to classify the types of messages. Appendix A classifies all messages using this scheme:",{"_35":870,"_37":4621,"_39":496,"_41":4622,"_66":4623,"_68":4624,"_70":69},"zcQHckiX",{"_273":323},[],"5.9. Protocol Summary",{"_35":870,"_37":4626,"_39":506,"_41":4627,"_66":4628,"_68":4629,"_70":69},"O8ktMcxS",{"_273":323},[],"5. Defining the OHP Protocol",{"_31":4631,"_33":4962},[4632,4639,4758,4877,4913,4941],{"_31":4633,"_33":4634},[],{"_35":160,"_37":4635,"_39":496,"_41":4636,"_66":4637,"_68":4638,"_70":69},"hop3SI-1",{},[],"In this section we consider, by reference to some different types of hypermedia viewer / editors, the way that these applications might use the OHP Protocol.",{"_31":4640,"_33":4753},[4641,4648,4655,4662,4669,4676,4683,4690,4697,4704,4711,4718,4725,4732,4739,4746],{"_31":4642,"_33":4643},[],{"_35":160,"_37":4644,"_39":496,"_41":4645,"_66":4646,"_68":4647,"_70":69},"mEDlADqR",{},[],"A Microcosm semi-aware viewer might be a program such as Word for Windows, which has been adapted, usually by the use of application specific macros, to allow the user to make selections and request actions. For the purpose of this example we will assume that we are not going to attempt to enable the application to handle persistent selections: in Microcosm terms this viewer will not handle buttons or specific links, but will allow the user to create local and generic links, and will allow the user to follow such links and to request other services such as computed links.",{"_31":4649,"_33":4650},[],{"_35":160,"_37":4651,"_39":496,"_41":4652,"_66":4653,"_68":4654,"_70":69},"XmPrkrwB",{},[],"Let us assume that in this case the user has been working in Word for Windows \"off-line\", and the scenario begins at the moment that the user decides that they wish to start using hypertext services.",{"_31":4656,"_33":4657},[],{"_35":160,"_37":4658,"_39":496,"_41":4659,"_66":4660,"_68":4661,"_70":69},"5oa-nKa0",{},[],"The user selects a menu option on Word asking to register with the link service. This menu might cause the following message to be sent to the link service:",{"_31":4663,"_33":4664},[],{"_35":2026,"_37":4665,"_39":496,"_41":4666,"_66":4667,"_68":4668,"_70":69},"0D_2WtD6",{"_2029":69},[]," \\Subject CreateNode \\DocumentName C:\\DOCS\\MYDOC.DOC \\DocumentType Word4Windows",{"_31":4670,"_33":4671},[],{"_35":160,"_37":4672,"_39":496,"_41":4673,"_66":4674,"_68":4675,"_70":69},"TXWBwh3e",{},[],"The Linkservice would check to see if it already knew about this document. If not, it would create a new record in the link database registering the document. Assuming that there were already 8 live connections to the link service, it might return the message:",{"_31":4677,"_33":4678},[],{"_35":2026,"_37":4679,"_39":496,"_41":4680,"_66":4681,"_68":4682,"_70":69},"3r2dgSVL",{"_2029":69},[],"\\Subject HeresNewChannel \\DocumentNickName Hugh's Comments On The Protocol\\SendDocument False \\Channel #9",{"_31":4684,"_33":4685},[],{"_35":160,"_37":4686,"_39":496,"_41":4687,"_66":4688,"_68":4689,"_70":69},"qhWO2BFN",{},[],"The viewer might now request the services",{"_31":4691,"_33":4692},[],{"_35":2026,"_37":4693,"_39":496,"_41":4694,"_66":4695,"_68":4696,"_70":69},"qsidBVYq",{"_2029":69},[],"\\Subject GetServices \\Channel #9",{"_31":4698,"_33":4699},[],{"_35":160,"_37":4700,"_39":496,"_41":4701,"_66":4702,"_68":4703,"_70":69},"JIDFCmca",{},[],"The linkservice would decide, which would now know the document type, and thus the viewer, and would return the appropriate available services, e.g. ",{"_31":4705,"_33":4706},[],{"_35":2026,"_37":4707,"_39":496,"_41":4708,"_66":4709,"_68":4710,"_70":69},"J4APMOhZ",{"_2029":69},[],"\\Subject HeresSubjects \\Data {\\Menuitem Follow Link\\Service FOLLOW.LINK} \\Data {\\Menuitem Show Links\\Service SHOW.LINKS} \\Data {\\Menuitem Compute Links\\Service COMPUTE.LINKS} \\Data {\\Menuitem Make Start Anchor\\Service START.LINK} \\Data {\\Menuitem Make End Anchor\\Service END.LINK} \\Channel #9",{"_31":4712,"_33":4713},[],{"_35":160,"_37":4714,"_39":496,"_41":4715,"_66":4716,"_68":4717,"_70":69},"iIXX_tgF",{},[],"The viewer on receiving this message would build a menu for the user to select these services. Since this viewer is not intended to be capable of handling persistent selections, no request will be sent to the link service for the anchor table.",{"_31":4719,"_33":4720},[],{"_35":160,"_37":4721,"_39":496,"_41":4722,"_66":4723,"_68":4724,"_70":69},"-5wwgAdU",{},[],"Now, a user might select the string \"making a menu\" within the document and select \"Make Start Anchor\" from the menu. The viewer will send the message:",{"_31":4726,"_33":4727},[],{"_35":2026,"_37":4728,"_39":496,"_41":4729,"_66":4730,"_68":4731,"_70":69},"QQuWO11r",{"_2029":69},[],"\\Subject RequestService \\Service START.LINK \\AnchorID \\LocSpec {\\ContentType ASCII\\Content making a menu\\Count \\ReverseCount \\Name \\Script } \\Presentation \\Channel #9",{"_31":4733,"_33":4734},[],{"_35":160,"_37":4735,"_39":496,"_41":4736,"_66":4737,"_68":4738,"_70":69},"7KISu2tT",{},[],"The link service, on receiving this message would note that no LocSpec information, other than the content, had been provided, and would thus start up the link making dialogue with options to create local or generic links. Note that the link making dialogue is within the province of the link service, and is not, currently, part of the OHP protocol.",{"_31":4740,"_33":4741},[],{"_35":160,"_37":4742,"_39":496,"_41":4743,"_66":4744,"_68":4745,"_70":69},"4IMj1y_U",{},[],"The user might continue to request further services in a similar way to the above, and then when finished would close the document, which action would cause the following message to be sent.",{"_31":4747,"_33":4748},[],{"_35":2026,"_37":4749,"_39":496,"_41":4750,"_66":4751,"_68":4752,"_70":69},"CRWWy0EI",{"_2029":69},[],"\\Subject Closing \\Channel #9",{"_35":870,"_37":4754,"_39":496,"_41":4755,"_66":4756,"_68":4757,"_70":69},"M_7FzUO1",{"_273":323},[],"6.1. A Microcosm Semi-Aware Viewer",{"_31":4759,"_33":4872},[4760,4767,4774,4781,4788,4795,4802,4809,4816,4823,4830,4837,4851,4858],{"_31":4761,"_33":4762},[],{"_35":160,"_37":4763,"_39":496,"_41":4764,"_66":4765,"_68":4766,"_70":69},"wEYy0Jfr",{},[],"Now let us consider the case of Word for Windows adapted as a fully aware Microcosm viewer. In this example perhaps the user follows a link to a node that is a Word for Windows document held on the network file system. Thus the linkservice might begin by sending the message:",{"_31":4768,"_33":4769},[],{"_35":2026,"_37":4770,"_39":496,"_41":4771,"_66":4772,"_68":4773,"_70":69},"uL87c8O4",{"_2029":69},[],"\\Subject LaunchDocument \\DocumentName N:\\docs\\file.doc \\ReadOnly False \\DocumentNickName \\DocumentType Word4Windows \\DataCallBack False \\Channel #10 ",{"_31":4775,"_33":4776},[],{"_35":160,"_37":4777,"_39":496,"_41":4778,"_66":4779,"_68":4780,"_70":69},"fUHM7TB_",{},[],"indicating that the linkservice wishes Word for Windows to be launched with the named document in editable mode. The linkservice has allocated channel 10. When word has been launched it will send back the messages:",{"_31":4782,"_33":4783},[],{"_35":2026,"_37":4784,"_39":496,"_41":4785,"_66":4786,"_68":4787,"_70":69},"b3kQlsWV",{"_2029":69},[],"\\Subject GetServices \\Channel #10 \\Subject GetAnchorTable \\Channel #10",{"_31":4789,"_33":4790},[],{"_35":160,"_37":4791,"_39":496,"_41":4792,"_66":4793,"_68":4794,"_70":69},"J6bdaAC4",{},[],"The linkservice might reply to this by sending the same HeresServices message as in the previous section, and also send the message:",{"_31":4796,"_33":4797},[],{"_35":2026,"_37":4798,"_39":496,"_41":4799,"_66":4800,"_68":4801,"_70":69},"ypoeR0Uy",{"_2029":69},[],"\\Subject HeresAnchorTable\n\\Data {\\AnchorID id_1 \\LocSpec {\\ContentType ASCII \\Content bank balance\n\\Count 1045 \\ReverseCount 2345 \\Name \\Script } \\Direction Start\n\\Presentation 1,1,1 \\Service FOLLOW.LINK}\n\\Data {\\AnchorID id_2 \\LocSpec {\\ContentType ASCII \\Content html editors\n\\Count 2085 \\ReverseCount 1305 \\Name \\Script } \\Direction Start\n\\Presentation 1,1,1 \\Service COMPUTE.LINKS}\n\\Data {\\AnchorID id_3 \\LocSpec {\\ContentType ASCII \\Content Dr Smith \\Count 3045 \\ReverseCount 345 \\Name \\Script } \\Direction End \\Presentation 1,1,2 \\Service Nil}\n\\Channel #10",{"_31":4803,"_33":4804},[],{"_35":160,"_37":4805,"_39":496,"_41":4806,"_66":4807,"_68":4808,"_70":69},"x_xB5iym",{},[],"In this example three link anchors are described. The first two are start anchors, and the third is a destination anchor (which has a service of Nil). The LocSpecs of these anchors describe the persistent selections in terms of byte offsets through the file, in both directions. An interesting problem arises here. Word can handle and save bookmarks, which would make an ideal method for representing persistent selections. However, if the user who is making links within the document does not have write permission for this document, then it will not be possible to save the document with the bookmarks embedded. For this reason the viewer is not attempting to save the bookmarks with the file, but is saving their position within the anchor's LocSpec, and might turn these positions into bookmarks during the period that the file is being viewed or edited.",{"_31":4810,"_33":4811},[],{"_35":160,"_37":4812,"_39":496,"_41":4813,"_66":4814,"_68":4815,"_70":69},"klI0lvJR",{},[],"The first thing that the viewer would need to do would be to put the bookmarks into the given positions. It will need to check that the content at these position does match the expected content, and if not it will need to apply some algorithm to find where the bookmarks should be placed.",{"_31":4817,"_33":4818},[],{"_35":160,"_37":4819,"_39":496,"_41":4820,"_66":4821,"_68":4822,"_70":69},"6cv4pKgD",{},[],"The linkservice might follow it original LaunchDocument request with:",{"_31":4824,"_33":4825},[],{"_35":2026,"_37":4826,"_39":496,"_41":4827,"_66":4828,"_68":4829,"_70":69},"Kp-yGkGS",{"_2029":69},[],"\\Subject DisplayLocSpec {\\ContentType ASCII \\Content Dr Smith \\Count 3045 \\ReverseCount 345 \\Name \\Script }\\Presentation 1,1,1\\Channel #10",{"_31":4831,"_33":4832},[],{"_35":160,"_37":4833,"_39":496,"_41":4834,"_66":4835,"_68":4836,"_70":69},"he7Yi9JD",{},[],"The viewer will now need to highlight the string \"Dr Smith\" and scroll the document so that this destination anchor is within view.",{"_31":4838,"_33":4846},[4839],{"_31":4840,"_33":4841},[],{"_35":2026,"_37":4842,"_39":496,"_41":4843,"_66":4844,"_68":4845,"_70":69},"MsFA6gDg",{"_2029":69},[],"\\Subject RequestService \\Service COMPUTE.LINKS \\AnchorID id_2\\LocSpec\\LocSpec {\\ContentType ASCII \\Content html editors \\Count 2085 \\ReverseCount 1305 \\Name \\Script }\\Presentation \\Channel #10",{"_35":160,"_37":4847,"_39":496,"_41":4848,"_66":4849,"_68":4850,"_70":69},"XX-Z32ct",{"_273":323},[],"Maybe the user now clicks on the bookmark over the string \"html editors\". In this case the viewer will send the message:",{"_31":4852,"_33":4853},[],{"_35":160,"_37":4854,"_39":496,"_41":4855,"_66":4856,"_68":4857,"_70":69},"J4eJD_bT",{},[],"This will cause the linkservice to apply the COMPUTE.LINKS service to the given LocSpec. Before the viewer is closed, it will be the responsibility of the viewer to send an UpdateAnchors message to the linkservice to ensure that all its LocSpecs coincide with the current position of the bookmarks.",{"_31":4859,"_33":4867},[4860],{"_31":4861,"_33":4862},[],{"_35":160,"_37":4863,"_39":496,"_41":4864,"_66":4865,"_68":4866,"_70":69},"y1VKWn-1",{},[],"Microcosm does not store anchorID's. A Microcosm link consists principally of the start and end LocSpecs. The anchor id's in the anchor table were inserted by the protocol shim for the sake of complying with the OHP protocol. Microcosm itself will never use them: it will communicate with the shim entirely in terms of LocSpecs, and will never send the DisplayAnchor message.2 It is important that the viewer does not make any assumption that the set of bookmarks it has at any particular time represents the entire set of available bookmarks. This is because Microcosm allows the installation of different sets of links (or Webs), and there may be other anchors within the document that are not currently available. This feature will be common to any distributed link service.",{"_35":160,"_37":4868,"_39":496,"_41":4869,"_66":4870,"_68":4871,"_70":69},"TmpMN89k",{"_273":2113},[],"Before leaving Microcosm, it is worth making two particular points.",{"_35":870,"_37":4873,"_39":496,"_41":4874,"_66":4875,"_68":4876,"_70":69},"fWJdgbeu",{"_273":323},[],"6.2. Microcosm fully aware",{"_31":4878,"_33":4908},[4879,4886,4893,4901],{"_31":4880,"_33":4881},[],{"_35":160,"_37":4882,"_39":496,"_41":4883,"_66":4884,"_68":4885,"_70":69},"18XTThHp",{},[],"Many of the classic Dexter systems expect that the application will own the anchor table. Such systems might store this table with the data, or might arrange to store the table outside the data in a separate but associated file. When a new anchor is created, its identifier is allocated by the viewer application and is unique within that context. The links that are stored within the linkservice have ends which consist of a (Document Name, AnchorID) pair. This situation can easily be handled by the OHP protocol as follows.",{"_31":4887,"_33":4888},[],{"_35":160,"_37":4889,"_39":496,"_41":4890,"_66":4891,"_68":4892,"_70":69},"seab4iO2",{},[],"The OHP protocol shim should be written to handle the storage and delivery of the anchor table for each document. Thus when the GetAnchorTable message is received by the protocol shim, it will retrieve the correct file (which it will identify from the channel information). The linkservice itself will never see this message. The viewer will communicate to the linkservice about anchors in terms of the anchorID and the channel (and perhaps the LocSpec), and the shim will convert this into messages about the anchorID and the document name, as shown in figure 3.",{"_31":4894,"_33":4895},[],{"_35":1875,"_37":4896,"_39":496,"_41":4897,"_66":4898,"_68":4899,"_70":4900},"5ZbX7sCS",{"_273":323},[],"Figure 3: Anchor Table Handling in Classic Dexter Systems.","ipfs://bafkreiccd6ui7qwoaq6nnyzca44eietbmrd4rch4qdisjctklr6jv562wy",{"_31":4902,"_33":4903},[],{"_35":160,"_37":4904,"_39":496,"_41":4905,"_66":4906,"_68":4907,"_70":69},"Z4O3xHeS",{},[],"Since such linkservices do not normally provide a service for allocating anchor identifiers, the protocol shim will need to provide the service instead. When the viewer sends a service request for a new anchor, the OHP shim will consult the appropriate anchor table and allocate the next available anchorID, which it will pass back to the viewer.",{"_35":870,"_37":4909,"_39":496,"_41":4910,"_66":4911,"_68":4912,"_70":69},"93qL0egP",{"_273":323},[],"6.3. Classic Dexter Systems",{"_31":4914,"_33":4936},[4915],{"_31":4916,"_33":4931},[4917,4924],{"_31":4918,"_33":4919},[],{"_35":160,"_37":4920,"_39":496,"_41":4921,"_66":4922,"_68":4923,"_70":69},"NYLLF08z",{},[],"They expect to allocate anchors that are globally unique, and they provide a service to allocate such identifiers. The linkservice must of course still know which document an anchor belongs within so that it can display the correct document when a link is followed to the anchor.",{"_31":4925,"_33":4926},[],{"_35":160,"_37":4927,"_39":496,"_41":4928,"_66":4929,"_68":4930,"_70":69},"C7fGFSrs",{},[],"They often expect to store the node contents. The protocol has the HeresDocument and Update node messages specially to deal with this case. In many cases the node contents may contain the (anchorID, LocSpec) table. If this is the case, the OHP protocol shim will need to arrange to separate the table from the raw node contents, so that the application may first load the contents, then call for the anchor table which will be sent on in a separate HeresAnchorTable message.",{"_35":160,"_37":4932,"_39":496,"_41":4933,"_66":4934,"_68":4935,"_70":69},"WGmAqqni",{"_273":2113},[],"Most hyperbase systems differ from the descriptions given so far in two respects:",{"_35":870,"_37":4937,"_39":496,"_41":4938,"_66":4939,"_68":4940,"_70":69},"2ASaK_R-",{"_273":323},[],"6.4. Hyperbase Systems",{"_31":4942,"_33":4957},[4943,4950],{"_31":4944,"_33":4945},[],{"_35":160,"_37":4946,"_39":496,"_41":4947,"_66":4948,"_68":4949,"_70":69},"qX3FfoyP",{},[],"Where a viewer is being specially built for a format that will only be used hypertext systems it is likely that the developer will specify data format in such a way that the persistent selections may be held as mark-up within the data. Such a format is htf used by Hyper-G. In such cases the anchorID will be encoded into the mark-up and passed to and from the link service to identify the ends of links. These anchorID's might be unique to the document or to the link service as a whole. It is important to realise, however, that not all the anchors held in the document will necessarily be currently valid. In many systems separate Webs of links may be installed, and the anchors that will be valid will depend on the choice of Web. ",{"_31":4951,"_33":4952},[],{"_35":160,"_37":4953,"_39":496,"_41":4954,"_66":4955,"_68":4956,"_70":69},"aVDiH6mF",{},[],"Therefore, if such a viewer is to work with the protocol it must still send the GetAnchorTable to the linkservice: only those anchors which the linkservice returns should be offered to the user.",{"_35":870,"_37":4958,"_39":496,"_41":4959,"_66":4960,"_68":4961,"_70":69},"HDslxcaB",{"_273":323},[],"6.5. Embedded Anchor Viewers",{"_35":870,"_37":4963,"_39":496,"_41":4964,"_66":4965,"_68":4966,"_70":69},"qBxlFUL3",{"_273":323},[],"6 . E x a m p l e S ce n a r i o s",{"_31":4968,"_33":5073},[4969,4997,5004,5053],{"_31":4970,"_33":4992},[4971,4978,4985],{"_31":4972,"_33":4973},[],{"_35":160,"_37":4974,"_39":506,"_41":4975,"_66":4976,"_68":4977,"_70":69},"hK7LgKdG",{},[],"how do we change the behaviour of the program so that it will send and receive the necessary messages? We can usually only achieve this is if the program has an internal macro language or else we can get access to the source code to extend its behaviour.",{"_31":4979,"_33":4980},[],{"_35":160,"_37":4981,"_39":506,"_41":4982,"_66":4983,"_68":4984,"_70":69},"kSaI300F",{},[],"how do we get the required information for the LocSpec? This requires that the application allows us to understand something about its data format.",{"_31":4986,"_33":4987},[],{"_35":160,"_37":4988,"_39":496,"_41":4989,"_66":4990,"_68":4991,"_70":69},"KEAHT_Rg",{},[],"how do we indicate the presence of anchors within the application data? This requires that we are able to alter the display characteristics of the application.",{"_35":160,"_37":4993,"_39":506,"_41":4994,"_66":4995,"_68":4996,"_70":69},"F8qBSlgQ",{"_273":274},[],"A question that has often been posed to the open hypermedia research community is, why do we not use existing standards such as OLE and CORBA? The usual answer has been that these standards do not provide the correct services, and anyway they are by no means standard across architectures, or are not in common use. It is worthwhile, however to consider at this point how existing and emerging standards might be of use in implementing an application to work with a protocol such as OHP. The prevailing problems, when it comes to hypertext enabling an application are:",{"_31":4998,"_33":4999},[],{"_35":160,"_37":5000,"_39":496,"_41":5001,"_66":5002,"_68":5003,"_70":69},"bkTvYojS",{},[],"Existing standards which are well worth noting are the Apple Event Object Model (AEOM) which is a Macintosh standard, and OpenDoc which is a multi-platform model which will shortly be able to interoperate with OLE.",{"_31":5005,"_33":5048},[5006,5013,5020,5027,5034,5041],{"_31":5007,"_33":5008},[],{"_35":160,"_37":5009,"_39":506,"_41":5010,"_66":5011,"_68":5012,"_70":69},"PspLi_0B",{},[],"The Apple Event Object Model (AEOM) consists of a number of standardised sets (or suites) of messages and abstract data objects, which are intended to cover both the inter-application exchange and manipulation of most forms of data, and the external control of applications.",{"_31":5014,"_33":5015},[],{"_35":160,"_37":5016,"_39":506,"_41":5017,"_66":5018,"_68":5019,"_70":69},"BVnk-mb2",{},[],"The Required Suite is a set of four basic messages which every Macintosh application is required to support. These are: Open Application, Open Document, Print Document and Quit Application.",{"_31":5021,"_33":5022},[],{"_35":160,"_37":5023,"_39":506,"_41":5024,"_66":5025,"_68":5026,"_70":69},"VCiURIdn",{},[],"The Core Suite must be supported by every AEOM compliant application. The messages allow chiefly for the retrieval and modification of data within applications, plus closing documents, and the making of selections.",{"_31":5028,"_33":5029},[],{"_35":160,"_37":5030,"_39":506,"_41":5031,"_66":5032,"_68":5033,"_70":69},"UUDieb2_",{},[],"Other suites are defined for specific data types, including text, pictures, tables, Quicklime and sound.",{"_31":5035,"_33":5036},[],{"_35":160,"_37":5037,"_39":506,"_41":5038,"_66":5039,"_68":5040,"_70":69},"vQo9Vxld",{},[],"Most suites define a set of objects to cover the data type that they handle. An application's data is arranged as a hierarchy of these objects. For example: at the top of the hierarchy is the \"application\" object. This will have a set of \"window\" elements. A window within an application can be specified by name, or by order: window 1 will be the frontmost, window 2 the second from the front, etc. A window has a number of properties, including name, position, bounding rectangle etc., and selection. It is therefore very easy to retrieve the user selection from the front window of any compliant application. Furthermore, the calling application can specify the form in which it wants the data: it can ask for the content of the selection, or for its offset and range, or for any other attributes that are applicable. If an application is unable to produce the data in the necessary type, it may substitute an alternative, but the form of data supplied is always specified in its reply.",{"_31":5042,"_33":5043},[],{"_35":160,"_37":5044,"_39":506,"_41":5045,"_66":5046,"_68":5047,"_70":69},"_5-ibzMR",{},[],"The AEOM is in many ways ideally suited for use with OHP. LocSpec requirements can be translated almost verbatim into AEOM queries, which can be sent to a target application. The application need not be written with any knowledge of OHP; it must simply be written to take full advantage of its own target platform. The AEOM is open to the creation of new suites, so an OHP suite can be defined and used to create applications with a higher level of awareness, using only established tools and techniques.",{"_35":870,"_37":5049,"_39":506,"_41":5050,"_66":5051,"_68":5052,"_70":69},"-F30Am4Z",{"_273":323},[],"7.1. The Apple Event Object Model",{"_31":5054,"_33":5068},[5055,5061],{"_31":5056,"_33":5057},[],{"_35":160,"_37":5058,"_39":496,"_41":5059,"_66":5060,"_68":3251,"_70":69},"VU3uvS6Y",{},[],{"_31":5062,"_33":5063},[],{"_35":160,"_37":5064,"_39":496,"_41":5065,"_66":5066,"_68":5067,"_70":69},"ZSP0kcVz",{},[],"OpenDoc includes the Open Scripting Architecture a highly versatile mechanism that includes an AEOM style communication architecture. Consequently the same kind of Shims that would work with the AEOM would work with properly built OpenDoc part editors, and hence with OpenDoc applications. OpenDoc is a multi-platform architecture, and if it is successful in establishing itself the implications are significant.",{"_35":870,"_37":5069,"_39":506,"_41":5070,"_66":5071,"_68":5072,"_70":69},"LwX9iqjz",{"_273":323},[],"7.2. OpenDoc",{"_35":870,"_37":5074,"_39":506,"_41":5075,"_66":5076,"_68":5077,"_70":69},"HbYIxv8Q",{"_273":323},[],"7. Existing Standards",{"_31":5079,"_33":5465},[5080,5087,5094,5129,5136],{"_31":5081,"_33":5082},[],{"_35":160,"_37":5083,"_39":496,"_41":5084,"_66":5085,"_68":5086,"_70":69},"Z3RHuK5a",{},[],"This paper has described the first draft of level 0 and level 1 of a protocol for client viewers to communicate with a link service. No doubt, as developers try to match the protocol to their own link service, deficiencies will emerge and enhancements will be required.",{"_31":5088,"_33":5089},[],{"_35":160,"_37":5090,"_39":496,"_41":5091,"_66":5092,"_68":5093,"_70":69},"qdWECjUi",{},[],"It is intended that almost any application may run as a level 0 viewer (launch and run with no hypertext), and that level one, as described here, will be the sort of functionality that should be possible to achieve by adapting third party applications. We envisage that level 2 of the protocol will be a much heavier weight implementation.",{"_31":5095,"_33":5124},[5096,5103,5110,5117],{"_31":5097,"_33":5098},[],{"_35":160,"_37":5099,"_39":496,"_41":5100,"_66":5101,"_68":5102,"_70":69},"w5CxQo4M",{},[],"The system described here is a fairly passive form of linkservice: clients send requests and get answers which they display. However, systems such as Multicard (Rizk & Sauter) which run server end scripts tend to be much more active, interacting with and changing the data in a node, updating the presentation characteristics, altering the menus interactively, etc. Such behaviour puts a greater onus on the application as there are a much larger number of link service requests that it must be able to handle. We envisage that such extensions will be in level 2 of the protocol.",{"_31":5104,"_33":5105},[],{"_35":160,"_37":5106,"_39":496,"_41":5107,"_66":5108,"_68":5109,"_70":69},"6P4NNx9H",{},[],"At present the protocol allows the passing of scripts, both to identify a persistent selection, and also as a message in its own right to carry out some process at the client end. At present the language of the script is not prescribed, and the linkservice must know what sort of script to dispatch to a particular viewer. It is possible that these scripts could be standardised in level 2 of the protocol.",{"_31":5111,"_33":5112},[],{"_35":160,"_37":5113,"_39":496,"_41":5114,"_66":5115,"_68":5116,"_70":69},"YmKkr5W3",{},[],"There are a number of other cases where the link service needs to communicate with the user. For example, as link anchors are identified it is necessary for the linkservice to send the user a dialogue for eliciting such information as the link attributes. Also, when a document is registered with the system the linkservice will need to be given the document attributes. Such dialogues will be highly dependant on the particular link service, but it is quite possible that the protocol could be extended to include the communication of these dialogues to some standard demon at the client end.",{"_31":5118,"_33":5119},[],{"_35":160,"_37":5120,"_39":496,"_41":5121,"_66":5122,"_68":5123,"_70":69},"dyVV9QSd",{},[],"The set of services which a link service can respond to is not defined by the protocol. It might be possible to identify a set of services that is a superset of all known systems. It is not clear, however that there is much benefit in this exercise.",{"_35":160,"_37":5125,"_39":496,"_41":5126,"_66":5127,"_68":5128,"_70":69},"0nu9pMEn",{"_273":2113},[],"There are a number of ways in which we can imagine the protocol expanding in the future.",{"_31":5130,"_33":5131},[],{"_35":160,"_37":5132,"_39":496,"_41":5133,"_66":5134,"_68":5135,"_70":69},"EH0ShBLD",{},[],"The best known hypertext system is without doubt the World Wide Web, and the standard html viewers played an important part in making the Web so popular. The Web does not currently use a link service, but there is plenty of research aimed at producing link services for the Web, e.g. the Distributed Link Service (Carr et al, 1995 ), and once the links are abstracted from the documents, then the Web will no longer be dependant on html to provide hypertext functionality. It will become possible to use any viewer. Perhaps this protocol could have a future in providing a standard interface to Web link services.",{"_31":5137,"_33":5460},[5138,5152,5173,5222,5243,5264,5285,5306,5341,5369],{"_31":5139,"_33":5147},[5140],{"_31":5141,"_33":5142},[],{"_35":2026,"_37":5143,"_39":506,"_41":5144,"_66":5145,"_68":5146,"_70":69},"qkTaojGT",{"_2029":69},[],"{\\ContentType \\Content \\Count [] \\ReverseCount []\\Name [] \\Script []} ",{"_35":870,"_37":5148,"_39":506,"_41":5149,"_66":5150,"_68":5151,"_70":69},"MW_Y5Vcp",{"_273":323},[],"LocSpec Definition",{"_31":5153,"_33":5168},[5154,5161],{"_31":5155,"_33":5156},[],{"_35":2026,"_37":5157,"_39":506,"_41":5158,"_66":5159,"_68":5160,"_70":69},"ziDGt20G",{"_2029":69},[],"\\Presentation",{"_31":5162,"_33":5163},[],{"_35":160,"_37":5164,"_39":506,"_41":5165,"_66":5166,"_68":5167,"_70":69},"egrFLTJR",{},[],"where the data that follows the presentation tag is opaque, and will be understood only by the viewer that created it in the first place.",{"_35":870,"_37":5169,"_39":506,"_41":5170,"_66":5171,"_68":5172,"_70":69},"Eh4FzMzI",{"_273":323},[],"Presentation Specification",{"_31":5174,"_33":5217},[5175,5196],{"_31":5176,"_33":5191},[5177,5184],{"_31":5178,"_33":5179},[],{"_35":160,"_37":5180,"_39":506,"_41":5181,"_66":5182,"_68":5183,"_70":69},"8j-xI5o7",{},[],"(messages that the linkserver sends to the client asking for some action.) ",{"_31":5185,"_33":5186},[],{"_35":2026,"_37":5187,"_39":496,"_41":5188,"_66":5189,"_68":5190,"_70":69},"8aR6NNXp",{"_2029":69},[],"\n\\Subject LaunchDocument \\DocumentName \\ReadOnly \\DocumentNickName []\n\\DocumentType \\DataCallBack \\Channel\n\\Subject DisplayAnchor \\AnchorID \\Presentation \\Channel\n\\Subject DisplayLocSpec \\LocSpec \\Presentation \\Channel \\Subject Interpret \\ScriptType \\Data {} \\Channel \\Subject CloseNode \\UpdateNode \\Channel\n",{"_35":870,"_37":5192,"_39":506,"_41":5193,"_66":5194,"_68":5195,"_70":69},"ZfzenBPb",{"_273":323},[],"Linkservice Requests",{"_31":5197,"_33":5212},[5198,5205],{"_31":5199,"_33":5200},[],{"_35":160,"_37":5201,"_39":496,"_41":5202,"_66":5203,"_68":5204,"_70":69},"BPrV2haC",{},[],"(messages that the linkserver sends in response to all client requests.)",{"_31":5206,"_33":5207},[],{"_35":2026,"_37":5208,"_39":496,"_41":5209,"_66":5210,"_68":5211,"_70":69},"02nnabm0",{"_2029":69},[],"\\Subject HeresServices \\Data {\\Menuitem\\Service }+ \\Channel \\Subject HeresDocument \\Data \\Channel \\Subject HeresAnchorTable \\Data {\\AnchorID \\LocSpec \\Direction \\Presentation \\Service}+ \\Channel \\Subject HeresNewAnchor \\Data {\\AnchorID \\LocSpec \\Direction \\Presentation \\Service} \\Channel \\Subject HeresNewChannel \\SendDocument \\DocumentNickName [] \\Channel",{"_35":870,"_37":5213,"_39":496,"_41":5214,"_66":5215,"_68":5216,"_70":69},"Bw_ATtvp",{"_273":323},[],"Linkservice Replies ",{"_35":870,"_37":5218,"_39":506,"_41":5219,"_66":5220,"_68":5221,"_70":69},"8CzL0Cra",{"_273":323},[],"Messages Classified by Type",{"_31":5223,"_33":5238},[5224,5231],{"_31":5225,"_33":5226},[],{"_35":160,"_37":5227,"_39":496,"_41":5228,"_66":5229,"_68":5230,"_70":69},"dub-sGh6",{},[],"(Messages that the client sends, typically at start-up, in order to initialise itself with the necessary linkservice information.)",{"_31":5232,"_33":5233},[],{"_35":2026,"_37":5234,"_39":496,"_41":5235,"_66":5236,"_68":5237,"_70":69},"gh1V1Dy7",{"_2029":69},[],"\\Subject GetNode \\DocumentName \\Channel\n\\Subject GetServices \\Channel\n\\Subject GetAnchorTable \\Channel\n\\Subject CreateNode \\DocumentName \\DocumentType \\Channel ",{"_35":870,"_37":5239,"_39":496,"_41":5240,"_66":5241,"_68":5242,"_70":69},"sGs72g5Z",{"_273":323},[],"Client Initialisation Requests",{"_31":5244,"_33":5259},[5245,5252],{"_31":5246,"_33":5247},[],{"_35":160,"_37":5248,"_39":496,"_41":5249,"_66":5250,"_68":5251,"_70":69},"MhlvlpW-",{},[],"(Messages that the client sends to the linkserver to inform the linkserver of changes to the linkservice information that have occurred at the client end.)",{"_31":5253,"_33":5254},[],{"_35":2026,"_37":5255,"_39":496,"_41":5256,"_66":5257,"_68":5258,"_70":69},"prTBEA1M",{"_2029":69},[]," \\Subject UpdateAnchors \\Data {\\AnchorID \\LocSpec \\Direction \\Presentation \\Service }+ \\Channel\n\\Subject UpdateNode \\DocumentType \\Data \\Channel\n\\Subject Closing \\Channel ",{"_35":870,"_37":5260,"_39":496,"_41":5261,"_66":5262,"_68":5263,"_70":69},"zuO6Th6z",{"_273":323},[],"Client Update Requests",{"_31":5265,"_33":5280},[5266,5273],{"_31":5267,"_33":5268},[],{"_35":160,"_37":5269,"_39":496,"_41":5270,"_66":5271,"_68":5272,"_70":69},"HE046ZCf",{},[],"(Messages that are sent when a sensitive area is clicked on, or a choice has been made from a link service supplied menu.)",{"_31":5274,"_33":5275},[],{"_35":2026,"_37":5276,"_39":496,"_41":5277,"_66":5278,"_68":5279,"_70":69},"NeCf07A9",{"_2029":69},[],"\\Subject RequestService \\Service \\AnchorID [] \\LocSpec [] \\Presentation \\Channel ",{"_35":870,"_37":5281,"_39":496,"_41":5282,"_66":5283,"_68":5284,"_70":69},"H0634xlq",{"_273":323},[],"Client Event Requests",{"_31":5286,"_33":5301},[5287,5294],{"_31":5288,"_33":5289},[],{"_35":160,"_37":5290,"_39":496,"_41":5291,"_66":5292,"_68":5293,"_70":69},"BQOCU8IH",{},[],"(Messages that are sent by the client in response to requests from the linkservice.)",{"_31":5295,"_33":5296},[],{"_35":160,"_37":5297,"_39":496,"_41":5298,"_66":5299,"_68":5300,"_70":69},"kMuP3lPu",{},[],"There are none in Level 1 of the Protocol",{"_35":870,"_37":5302,"_39":496,"_41":5303,"_66":5304,"_68":5305,"_70":69},"dCXpzFcw",{"_273":323},[],"Client Replies",{"_31":5307,"_33":5336},[5308,5315,5322,5329],{"_31":5309,"_33":5310},[],{"_35":160,"_37":5311,"_39":496,"_41":5312,"_66":5313,"_68":5314,"_70":69},"e1bz-kck",{},[],"(Messages that may be sent either way. )",{"_31":5316,"_33":5317},[],{"_35":2026,"_37":5318,"_39":496,"_41":5319,"_66":5320,"_68":5321,"_70":69},"SBGQhXsq",{"_2029":69},[],"\\Subject Error \\ErrorSubject \\ErrorMessage \\Channel \\Subject Other \\UserDefinedTag +\\Channel Channel",{"_31":5323,"_33":5324},[],{"_35":160,"_37":5325,"_39":496,"_41":5326,"_66":5327,"_68":5328,"_70":69},"CLQaD-3X",{},[],"There may also be an optional extra tag on the end of any message.",{"_31":5330,"_33":5331},[],{"_35":2026,"_37":5332,"_39":496,"_41":5333,"_66":5334,"_68":5335,"_70":69},"k3HPkoNu",{"_2029":69},[],"\\Other",{"_35":870,"_37":5337,"_39":496,"_41":5338,"_66":5339,"_68":5340,"_70":69},"j6vkkbGY",{"_273":323},[],"Bi-directional Messages",{"_31":5342,"_33":5364},[5343,5350,5357],{"_31":5344,"_33":5345},[],{"_35":160,"_37":5346,"_39":496,"_41":5347,"_66":5348,"_68":5349,"_70":69},"zttnABdq",{},[],"Level 0: Only Supports LaunchDocument and CloseNode messages from linkserver to client. No communication. No hypertext. Any application should be able to run as a Level 0 viewer.",{"_31":5351,"_33":5352},[],{"_35":160,"_37":5353,"_39":506,"_41":5354,"_66":5355,"_68":5356,"_70":69},"H6a1MfNi",{},[],"Level 1: Supports the functionality described in this paper. It is intended that it will be possible to achieve this level by adapting third party applications.",{"_31":5358,"_33":5359},[],{"_35":160,"_37":5360,"_39":496,"_41":5361,"_66":5362,"_68":5363,"_70":69},"MP_q7kK2",{},[],"Level 2: Not yet defined, but envisaged to support extensions to deal with content manipulation, presentation and standard client end scripts. It is expected that this level of conformity will only be achieved by writing specialised applications.",{"_35":870,"_37":5365,"_39":496,"_41":5366,"_66":5367,"_68":5368,"_70":69},"U0B6Orik",{"_273":323},[],"Levels of the Protocol",{"_31":5370,"_33":5455},[5371,5399],{"_31":5372,"_33":5394},[5373],{"_31":5374,"_33":5389},[5375,5382],{"_31":5376,"_33":5377},[],{"_35":160,"_37":5378,"_39":496,"_41":5379,"_66":5380,"_68":5381,"_70":69},"rGoxQlwX",{},[],"Accept Messages from Link Server, convert to OHP equivalent and pass to correct Client. ",{"_31":5383,"_33":5384},[],{"_35":160,"_37":5385,"_39":496,"_41":5386,"_66":5387,"_68":5388,"_70":69},"_KOFZrZE",{},[],"Accept Messages from Client side in OHP, convert and pass to link service in private protocol.",{"_35":160,"_37":5390,"_39":496,"_41":5391,"_66":5392,"_68":5393,"_70":69},"zXVTsk5Z",{"_273":274},[],"(Produced by Link Service suppliers).",{"_35":870,"_37":5395,"_39":496,"_41":5396,"_66":5397,"_68":5398,"_70":69},"MKcqfXBG",{"_273":323},[],"Server Side Protocol Shim.",{"_31":5400,"_33":5450},[5401],{"_31":5402,"_33":5445},[5403,5410,5417,5424,5431,5438],{"_31":5404,"_33":5405},[],{"_35":160,"_37":5406,"_39":496,"_41":5407,"_66":5408,"_68":5409,"_70":69},"LxyIJCDw",{},[],"Accept OHP messages from network and communicate message to correct viewer/editor.",{"_31":5411,"_33":5412},[],{"_35":160,"_37":5413,"_39":496,"_41":5414,"_66":5415,"_68":5416,"_70":69},"rqP80jv3",{},[],"Accept Messages from viewer editor and forward to linkservice in network protocol.",{"_31":5418,"_33":5419},[],{"_35":160,"_37":5420,"_39":496,"_41":5421,"_66":5422,"_68":5423,"_70":69},"D2MtuHoO",{},[],"Maintain table of applications on this platform which should be used for each data type.",{"_31":5425,"_33":5426},[],{"_35":160,"_37":5427,"_39":496,"_41":5428,"_66":5429,"_68":5430,"_70":69},"jtGLuZAm",{},[],"Maintain table showing what level of protocol can be expected from each viewer/editor.",{"_31":5432,"_33":5433},[],{"_35":160,"_37":5434,"_39":496,"_41":5435,"_66":5436,"_68":5437,"_70":69},"yY-px8pe",{},[],"Handle LaunchDocument messages at the client end, and, if a DataCallBack is required, send the GetNode message and handle the transfer of the data from the HeresDocument message to the application.",{"_31":5439,"_33":5440},[],{"_35":160,"_37":5441,"_39":496,"_41":5442,"_66":5443,"_68":5444,"_70":69},"cpcm_atW",{},[],"For level 0 applications, handle CloseNode messages, and return error messages for other linkservice requests.",{"_35":160,"_37":5446,"_39":496,"_41":5447,"_66":5448,"_68":5449,"_70":69},"vD5ASZKl",{"_273":274},[],"(One needs to be produced for each client platform, for each communication protocol conversion) ",{"_35":870,"_37":5451,"_39":496,"_41":5452,"_66":5453,"_68":5454,"_70":69},"UgIKkPOM",{"_273":323},[],"Client Side Communication Shim.",{"_35":870,"_37":5456,"_39":496,"_41":5457,"_66":5458,"_68":5459,"_70":69},"dyBrM8Y-",{"_273":323},[],"Responsibilities of the Shims",{"_35":870,"_37":5461,"_39":506,"_41":5462,"_66":5463,"_68":5464,"_70":69},"uNKh-KMA",{"_273":323},[],"Appendix: Summary of Protocol",{"_35":870,"_37":5466,"_39":506,"_41":5467,"_66":5468,"_68":5469,"_70":69},"yyLOxegg",{"_273":323},[],"8 . Conclusions",{"_31":5471,"_33":5549},[5472,5479,5486,5493,5500,5507,5514,5521,5528,5535,5542],{"_31":5473,"_33":5474},[],{"_35":160,"_37":5475,"_39":506,"_41":5476,"_66":5477,"_68":5478,"_70":69},"uu64jzAB",{},[],"Andrews K., Kappe, F. & Maurer, H. Hyper-G: Towards the Next Generation of Network Information Technology. Journal of Universal Computer Science, April 1995. Aßfalg, R. (ed.). The Proceedings of the Workshop on Open Hypertext Systems, Konstanz , May 1994. Carr, L.A., De Roure, D., Hall, W. & Hill, G.J. The Distributed Link Service: A Tool for Publishers, Authors and Readers. In: The Fourth International World Wide Web Conference Proceedings. pp 647-656. O'Reilly & Associates, Dec 1995.",{"_31":5480,"_33":5481},[],{"_35":160,"_37":5482,"_39":506,"_41":5483,"_66":5484,"_68":5485,"_70":69},"Bui7onmX",{},[],"Davis, H.C., Hall, W., Heath, I., Hill, G. & Wilkins, R. Towards an Integrated Information Environment with Open Hypermedia Systems . In: D. Lucarella, J. Nanard, M. Nanard, P. Paolini. eds. The Proceedings of the ACM Conference on Hypertext, ECHT '92 Milano , pp 181-190. ACM Press, 1992. Davis, H.C., Knight, S.K. & Hall, W. Light Hypermedia Link Services: A Study in Third Party Application Integration. In: The ACM Conference on Hypermedia Technology, ECHT '94 Proceedings. pp 41-50. ACM. Sept. 1994.",{"_31":5487,"_33":5488},[],{"_35":160,"_37":5489,"_39":506,"_41":5490,"_66":5491,"_68":5492,"_70":69},"szOoenx9",{},[],"Davis, H.C. To Embed or Not to Embed..., Communications of the ACM, Vol 38(8), pp 108-109. August 1995. DeRose, S.J & Durand, D.G. Making Hypermedia Work: A User's Guide to HyTime. Kluwer Academic Press. 1994",{"_31":5494,"_33":5495},[],{"_35":160,"_37":5496,"_39":506,"_41":5497,"_66":5498,"_68":5499,"_70":69},"JeV6f9Uf",{},[],"Grønbæk, K. & Trigg, R.H. Design Issues for a Dexter-Based Hypermedia System.",{"_31":5501,"_33":5502},[],{"_35":160,"_37":5503,"_39":506,"_41":5504,"_66":5505,"_68":5506,"_70":69},"VwGtQeuq",{},[],"In: D. Lucarella, J. Nanard, M. Nanard, P. Paolini. eds. The Proceedings of the ACM Conference on Hypertext, ECHT '92 Milano , pp 191- 200. ACM Press. Nov. 1992",{"_31":5508,"_33":5509},[],{"_35":160,"_37":5510,"_39":506,"_41":5511,"_66":5512,"_68":5513,"_70":69},"n4bVQ-I7",{},[],"Grønbæk, K. & Trigg, R.H. From Embedded References to Link Objects: Toward a New Data Model for Open Hypermedia Systems . To be published in The Proceedings of Hypertext '96. ACM 1996 Halasz, F. & Mayer, S. (edited by Grønbæk, K. & Trigg, R.H). The Dexter Hypertext Reference Model. Communications of the ACM. pp 30-39. 37(2). Feb. 1994.",{"_31":5515,"_33":5516},[],{"_35":160,"_37":5517,"_39":506,"_41":5518,"_66":5519,"_68":5520,"_70":69},"hn194sda",{},[],"Hall, W. Ending the Tyranny of the Button . IEEE Multimedia 1(1). 1994. Kacmar, C.J. & Leggett, J.J. PROXHY: A Process-Oriented Extensible Hypertext Architecture. ACM Trans. on Information Systems, 9(4) pp 299-419. Oct. 1991.",{"_31":5522,"_33":5523},[],{"_35":160,"_37":5524,"_39":506,"_41":5525,"_66":5526,"_68":5527,"_70":69},"gsQt9h5j",{},[],"Leggett, J. & Schnase, J. Dexter with Open Eyes. Communications of the ACM 37(2) pp 77-86. Feb. 1994 Østerbye, K. & Wiil, U.K. The Flag Taxonomy of Open Hypermedia Systems , To be published in The Proceedings of Hypertext '96. ACM 1996",{"_31":5529,"_33":5530},[],{"_35":160,"_37":5531,"_39":506,"_41":5532,"_66":5533,"_68":5534,"_70":69},"hDBTjTGw",{},[],"Rizk, A. The M2000 Protocol Description Manual. Euroclid. (Available from the author) 1991 Rizk, A. & Sauter, L. Multicard: An Open Hypermedia System .",{"_31":5536,"_33":5537},[],{"_35":160,"_37":5538,"_39":506,"_41":5539,"_66":5540,"_68":5541,"_70":69},"J-gjRiC1",{},[],"In: D. Lucarella, J. Nanard, M. Nanard, P. Paolini. eds. The Proceedings of the ACM Conference on Hypertext, ECHT '92 Milano , Italy, December 1992, pp 181-190. ACM Press. 1992",{"_31":5543,"_33":5544},[],{"_35":160,"_37":5545,"_39":506,"_41":5546,"_66":5547,"_68":5548,"_70":69},"fBKr4OEO",{},[],"Wiil, U.K & Østerbye, K. (eds.). The Proceedings of the ECHT '94 Workshop on Open Hypermedia Systems, Edinburgh, Sept. 1994. Technical Report R-94-2038. Aalborg University. Oct. 1994. Wiil, U.K. & Leggett, J.L. The HyperDisco Approach to Open Hypermedia Systems , To be published in The Proceedings of Hypertext '96. ACM 1996. View publication stats",{"_35":870,"_37":5550,"_39":506,"_41":5551,"_66":5552,"_68":3495,"_70":69},"w-3vrZyX",{"_273":323},[],[279],"/records/ohp-a-draft-proposal-for-a-standard-open-hypermedia-protocol-levels-0-and-1-revision-12","2025-07-07T17:52:01.543Z",{"_82":515},{},{"_37":493,"_95":53,"_54":5559,"_71":496,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,495],1772031973309,[149,493,496],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/ohp-a-draft-proposal-for-a-standard-open-hypermedia-protocol-levels-0-and-1-revision-12\",\"bafy2bzacecedtpecy4ftuuwgtjvkrevoht3qxodvaju3u5ia4k4fawg24hsy6\"]",{"_110":5564,"_147":5807,"_150":5808},{"_112":5565,"_131":132,"_133":5806,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":5566,"_37":5804},{"_28":5567,"_71":521,"_72":53,"_73":5800,"_54":5801,"_76":528,"_78":528,"_80":5802,"_84":5803,"_86":521,"_88":89},[5568,5581,5595,5602,5615],{"_31":5569,"_33":5570},[],{"_35":160,"_37":5571,"_39":521,"_41":5572,"_66":5573,"_68":5580,"_70":69},"O1VnU70U",{},[5574],{"_35":204,"_167":5575,"_169":5577,"_41":5578,"_70":5579},[5576],69,[1699],{},"mailto:halasz@xerox.com","Frank G. Halasz \nXerox PARC 3333 Coyote Hill Rd. Palo Alto, CA 94304 halasz@xerox.com ",{"_31":5582,"_33":5583},[],{"_35":160,"_37":5584,"_39":521,"_41":5585,"_66":5586,"_68":5594,"_70":69},"g_AU3JzO",{},[5587],{"_35":204,"_167":5588,"_169":5590,"_41":5592,"_70":5593},[5589],75,[5591],103,{},"mailto:mayers@tekchips.labs.tek.com","Mayer Schwartz \nTektronix Labs P.O. Box 500, MS 50-662 Beaverton, OR 97077 mayers@tekchips.labs.tek.com",{"_31":5596,"_33":5597},[],{"_35":160,"_37":5598,"_39":521,"_41":5599,"_66":5600,"_68":5601,"_70":69},"TbcpFJqr",{},[],"Presented at the NIST Hypertext Standardization Workshop, Gaithersburg, MD, January 16-18, 1990",{"_31":5603,"_33":5611},[5604],{"_31":5605,"_33":5606},[],{"_35":160,"_37":5607,"_39":521,"_41":5608,"_66":5609,"_68":5610,"_70":69},"QvM_1C90",{},[]," This paper presents the Dexter hypertext reference model. The Dexter model is an attempt to capture, both formally and informally, the important abstractions found in a wide range of existing and future hypertext systems. The goal of the model is to provide a principled basis for comparing systems as well as for developing interchange and interoperability standards. The model is divided into three layers. The storage layer describes the network of nodes and links that is the essence of hypertext. The runtime layer describes mechanisms supporting the user’s interaction with the hypertext. The within-component layer covers the content and structures within hypertext nodes. The focus of the model is on the storage layer as well as on the mechanisms of anchoring and presentation specification that form the interfaces between the storage layer and the within-component and runtime layers, respectively. The model is formalized in the specification language Z [Spiv89], a specification language based on set theory. The paper briefly discusses the issues involved in comparing the characteristics of existing systems against the model.",{"_35":870,"_37":5612,"_39":521,"_41":5613,"_66":5614,"_68":1827,"_70":69},"O4r43Akn",{"_273":323},[],{"_31":5616,"_33":5796},[5617,5624,5631,5638,5645,5652,5659,5666],{"_31":5618,"_33":5619},[],{"_35":160,"_37":5620,"_39":521,"_41":5621,"_66":5622,"_68":5623,"_70":69},"67dBmgVd",{},[],"What do hypertext1 systems such as NoteCards [Hala88], Neptune [Deli86a], KMS [Aksc88a], Intermedia [Yank88a] and Augment [Enge84a] have in common? How do they differ? In what way do these systems differ from related classes of systems such as multimedia database systems. At a very abstract level, each of these hypertext systems provides its users with the ability to create, manipulate, and/or examine a network of information-containing nodes interconnected by relational links. Yet these systems differ markedly in the specific data models and sets of functionality that they provide to their users. Augment, Intermedia, NoteCards, and Neptune, for example, all provide their users with a universe of arbitrary-length documents. KMS and Hypercard, in contrast, are built around a model of a fixed-size canvas onto which items such as text and graphics can be placed. Given these two radically different designs, is there anything common between these systems in their notions of hypertext nodes?",{"_31":5625,"_33":5626},[],{"_35":160,"_37":5627,"_39":521,"_41":5628,"_66":5629,"_68":5630,"_70":69},"uLhw6-Gk",{},[],"In an attempt to provide a principled basis for answering these questions, this paper presents the Dexter hypertext reference model. The model provides a standard hypertext terminology coupled with a formal model of the important abstractions commonly found in a wide range of hypertext systems. Thus, the Dexter model serves as a standard against which to compare and contrast the characteristics and functionality of various hypertext (and non-hypertext) systems. The Dexter model also serves as a principled basis on which to develop standards for interoperability and interchange among hypertext systems.",{"_31":5632,"_33":5633},[],{"_35":160,"_37":5634,"_39":521,"_41":5635,"_66":5636,"_68":5637,"_70":69},"QMwCL0Os",{},[],"The Dexter reference model described in this paper was initiated as the result of two small workshops on hypertext. The first workshop was held in October, 1988 at the Dexter Inn in New Hampshire. Hence the name of the model. The workshops had representatives from many of the major existing hypertext systems2 . A large part of the discussion at these workshops was the elicitation of the abstractions common to the major hypertext systems. The Dexter model is an attempt to capture, fill-out, and formalize the results of these discussions.",{"_31":5639,"_33":5640},[],{"_35":160,"_37":5641,"_39":521,"_41":5642,"_66":5643,"_68":5644,"_70":69},"HtuCDAZu",{},[],"Another important focus of the workshops was an attempt to find a common terminology for the hypertext field. This turned out to be an extremely difficult task, especially so in the absence of an understanding of the common (and differing) abstractions among the various systems. The term \"node\" turned out to be especially difficult given the extreme variation in the use of the term across the various systems. By providing a well-defined set of named abstractions, the Dexter model provides a solution to the hypertext terminology problem. It does so, however, at some cost. In order to avoid confusion, the model does not use contentious terms such as \"node\", prefering neutral terms such as \"component\" for the abstraction in the model.",{"_31":5646,"_33":5647},[],{"_35":160,"_37":5648,"_39":521,"_41":5649,"_66":5650,"_68":5651,"_70":69},"mPXwVQ68",{},[],"In the present paper, the Dexter model is formulated in Z [Spiv89], a formal specification language based on typed set theory. The use of Z provides a rigorous basis for defining the necessary abstractions and for discussing their use and interrelationships. Although an understanding of the Z language is a prerequisite for fully understanding the details of the Dexter model as described in this paper, the paper attempts to provide a complete description of the model in the prose accompanying the formal specification. Readers unfamiliar with Z should be able to gain a full, if not precisely detailed, understanding of the model.",{"_31":5653,"_33":5654},[],{"_35":160,"_37":5655,"_39":521,"_41":5656,"_66":5657,"_68":5658,"_70":69},"jz3CQvfM",{},[],"This paper also refers in passing to architectural concepts found in a number of existing hypertext systems including Augment [Enge84a], Concordia/Document Examiner [Walk88a], Hypercard [Good87], Hyperties [Shne89d], IGD [Fein82], Intermedia [Yank88a], KMS [Aksc88a], Neptune/HAM [Deli86a], NoteCards [Hala88], the Sun Link Service [Pear89], and Textnet [Trig86a]. The reader is assumed to be familiar with the general characteristics and functionality of these systems. Appropriate background material on these systems can be found in Conklin [Conk87a] and in the proceedings of the Hypertext 87 [HT87] and Hypertext 89 [HT89] conferences.",{"_31":5660,"_33":5661},[],{"_35":160,"_37":5662,"_39":521,"_41":5663,"_66":5664,"_68":5665,"_70":69},"_tHbzoNN",{},[],"This paper is divided in 4 main sections. The first section provides a brief discursive overview of the entire model. The second section describes the storage layer of the model, both formally and informally. The third section describes the runtime layer of the model in a similar manner. The final section discusses issues involved in comparing existing systems against the model.",{"_31":5667,"_33":5791},[5668,5675,5691,5698,5705,5712,5719,5726,5734,5741,5748,5756,5763,5770,5777,5784],{"_31":5669,"_33":5670},[],{"_35":160,"_37":5671,"_39":521,"_41":5672,"_66":5673,"_68":5674,"_70":69},"KQIktB_7",{},[],"The Dexter model divides a hypertext system into three layers, the runtime layer, the storage layer and the within-component layer, as illustrated in Figure 1. The main focus of the model is on the storage layer, which models the basic node/link network structure that is the essence of hypertext. The storage layer describes a ‘database’ that is composed of a hierarchy of data-containing ‘‘components’’ which are interconnected by relational ‘‘links’’. Components correspond to what is typically thought of as nodes in a hypertext network: cards in NoteCards and HyperCard, frames in KMS, documents in Augment and Intermedia, or articles in Hyperties.",{"_31":5676,"_33":5686},[5677],{"_31":5678,"_33":5679},[],{"_35":1875,"_37":5680,"_39":521,"_41":5681,"_66":5683,"_68":5684,"_70":5685},"UhAatK9O",{"_273":323,"_2135":5682},664.6408839779006,[],"Figure 1: Layers of the Dexter model.","ipfs://bafkreibnw37tecfx6yw7ffxl4c6gl6mg66r4d2eyex2eyyyja6jjzkeghy",{"_35":160,"_37":5687,"_39":521,"_41":5688,"_66":5689,"_68":5690,"_70":69},"Qjj1XFW-",{"_273":323},[],"Components contain the chunks of text, graphics, images, animations, etc. that form the basic content in the hypertext network",{"_31":5692,"_33":5693},[],{"_35":160,"_37":5694,"_39":521,"_41":5695,"_66":5696,"_68":5697,"_70":69},"KWB89_8l",{},[],"The storage layer focuses on the mechanisms by which the components and links are ‘‘glued together’’ to form hypertext networks. The components are treated in this layer as generic containers of data. No attempt is made to model any structure within the container. Thus, the storage layer makes no differentiation between text components and graphics components. Nor does it provide any mechanisms for dealing with the well-defined structure inherent within a structured document (e.g., an ODA document) component.",{"_31":5699,"_33":5700},[],{"_35":160,"_37":5701,"_39":521,"_41":5702,"_66":5703,"_68":5704,"_70":69},"jQW7-33r",{},[],"In contrast, the within-component layer of the model is specifically concerned with the contents and structure within the components of the hypertext network. This layer is purposefully not elaborated within the Dexter model. The range of possible content/structure that can be included in a component is open-ended. Text, graphics, animations, simulations, images, and many more types of data have been used as components in existing hypertext systems. It would be folly to attempt a generic model covering all of these data types. Instead, the Dexter model treats within-component structure as being outside of the hypertext model per se. It is assumed that other reference models designed specifically to model the structure of particular applications, documents, or data types (ODA, IGES, etc) will be used in conjunction with the Dexter model to capture the entirety of the hypertext, including the with-component content and structure.",{"_31":5706,"_33":5707},[],{"_35":160,"_37":5708,"_39":521,"_41":5709,"_66":5710,"_68":5711,"_70":69},"Xmgt1f6M",{},[],"An extremely critical piece of the Dexter model, however, is the interface between the hypertext network and the within-component content and structure. The hypertext system requires a mechanism for addressing (refering to) locations or items within the content of an individual component. In the Dexter model, this mechanism is know as anchoring. The anchoring mechanism is necessary, for example, to support span-to-span links such as are found in Intermedia. In Intermedia, the components are complete structured documents. Links are possible not only between documents, but between spans of characters within one document and spans of characters within another document. Anchors are a mechanism that provides this functionality while maintaining a clean separation between the storage and within-component layers.",{"_31":5713,"_33":5714},[],{"_35":160,"_37":5715,"_39":521,"_41":5716,"_66":5717,"_68":5718,"_70":69},"i_ejeA_h",{},[],"The storage and within-component layers treat hypertext as an essentially passive data structure. Hypertext systems, however, go far beyond this in the sense that they provide tools for the user to access, view, and manipulate the network structure. This functionality is captured by the runtime layer of the model. As in the case of within-component structure, the range of possible tools for accessing, viewing, and manipulating a hypertext networks is far too broad and too diverse to allow a simple, generic model. Hence the Dexter model provides only a bare-bones model of the mechanism for presenting a hypertext to the user for viewing and editing. This presentation mechanism captures the essentials of the dynamic, interactional aspects of hypertext systems, but it does not attempt to cover the details of user interaction with the hypertext.",{"_31":5720,"_33":5721},[],{"_35":160,"_37":5722,"_39":521,"_41":5723,"_66":5724,"_68":5725,"_70":69},"n6TUoz0E",{},[],"As in the case of anchoring, a critical aspect of the Dexter model is the interface between the storage layer and the runtime layer. In the Dexter model this is accomplished using the notion of presentation specifications. Presentation specifications are a mechanism by which information about how a component/network is to be presented to the user can be encoded into the hypertext network at the storage layer. Thus, the way in which a component is presented to the user can be a function not only of the specific hypertext tool that is doing the presentation (i.e., the specific runtime layer), but can also be a property of the component itself and/or of the access path (link) taken to that component.",{"_31":5727,"_33":5728},[],{"_35":1875,"_37":5729,"_39":521,"_41":5730,"_66":5731,"_68":5732,"_70":5733},"GjYBwNIh",{"_273":323},[],"Figure 2: Illustration of the need for presentation specifications on the access\npath (i.e., links) as well as on the components themselves.","ipfs://bafkreidlfepnod62ggwejjcwdist4xs474qozxl4pz6lc565jeqdc7qooq",{"_31":5735,"_33":5736},[],{"_35":160,"_37":5737,"_39":521,"_41":5738,"_66":5739,"_68":5740,"_70":69},"Ndk4eS-H",{},[],"Figure 2 illustrates the importance of the presentation specifications mechanism. In this figure, there is an animation component taken from a computer-based training hypertext. This animation component can be accessed from two other components, a ‘‘teacher’’ component and a ‘‘student’’ component. When following the link from the student component, the animation should be brought up as a running animation. In contast, when coming from the teacher component, the animation should be brought up in editing mode ready to be altered. In order to separate these two cases, the runtime layer needs to access presentation information encoded into the links in the network. Presentation specifications are a generic way of doing just this. Like anchoring, it is an interface that allows the storage layer to communicate in generic way with the runtime layer without violating the separation between the two layers.",{"_31":5742,"_33":5743},[],{"_35":160,"_37":5744,"_39":521,"_41":5745,"_66":5746,"_68":5747,"_70":69},"rLJuDEzf",{},[],"Figure 3 attempts to give a flavor of the various layers of the Dexter model as they are embedded within an typical hypertext system. The figure depicts a 3 node/1 link hypertext network. The storage layer contains four entities: the three components (i.e., nodes) and the link. The actual contents (text and graphics) for the components are located to the right of the storage layer in the within-components layer. In the runtime layer, the single graphics component is being presented to the user. The link emanating from this node is marked by an arrowhead located near the bottom of the node’s window on the computer screen.",{"_31":5749,"_33":5750},[],{"_35":1875,"_37":5751,"_39":521,"_41":5752,"_66":5753,"_68":5754,"_70":5755},"JDKn59RP",{"_273":323},[],"Figure 3: A depiction of the three layers of the Dexter model as embedded in an actual hypertext system","ipfs://bafkreift6npwkc7u65ylrgkhsujwccuf7whp624q2wdpbdebkrkozvezhi",{"_31":5757,"_33":5758},[],{"_35":160,"_37":5759,"_39":521,"_41":5760,"_66":5761,"_68":5762,"_70":69},"mjp75l-q",{},[],"another composite is restricted to be a direct-acyclic graph (DAG), i.e., no composite may contain itself either directly or indirectly. Composite components are relative rare in the current generation of hypertext systems. One exception is the Augment system where a document is a tree-structured composition of atomic components called statements.",{"_31":5764,"_33":5765},[],{"_35":160,"_37":5766,"_39":521,"_41":5767,"_66":5768,"_68":5769,"_70":69},"SdbXKAFG",{},[],"Every component has a globally unique identity which is captured by its unique identifier (UID). UIDs are primitive in the model, but they are assumed to be uniquely assigned to components across the entire universe of discourse (not just within the context of a single hypertext). The accessor function of the hypertext is responsible for ‘‘accessing’’ a component given its UID, i.e., for mapping a UID into the component ‘‘assigned’’ that UID.",{"_31":5771,"_33":5772},[],{"_35":160,"_37":5773,"_39":521,"_41":5774,"_66":5775,"_68":5776,"_70":69},"OaqNEsjR",{},[],"UIDs provide a guaranteed mechanism for addressing any component in a hypertext. But the use of UIDs as a basic addressing mechanism in hypertext may be too restrictive. For example, it is possible in the Augment system to create a link to ‘‘the statement containing the word ‘pollywog’’’. The statement specified by this link may not exist or it may change over time as documents are edited. Therefore, the link cannot rely on a specific statement UID to address the target statement. Rather, when the link is followed, the specification must be ‘‘resolved’’ to a UID (if possible), which then can be used to access the correct component.",{"_31":5778,"_33":5779},[],{"_35":160,"_37":5780,"_39":521,"_41":5781,"_66":5782,"_68":5783,"_70":69},"iVVivgaj",{},[],"This kind of indirect addressing is supported in the storage layer using component specifications together with the resolver function. The resolver function is responsible for ‘‘resolving’’ a component specification into a UID, which can then be fed to the accessor function to retrieve the specified component. Note, however, that the resolver function is only a partial function. A given specification may not be resolvable into a UID, i.e., the component being specified may not exist. However, it is the case that for every component there is at least one specification that will resolve to the UID for that component. In particular, the UID itself may be used as a specifier, in which case the resolver function is the identity function.",{"_31":5785,"_33":5786},[],{"_35":160,"_37":5787,"_39":521,"_41":5788,"_66":5789,"_68":5790,"_70":69},"impMCGiY",{},[],"Implementing span-to-span links (e.g., in Intermedia) requires more than simply specifying entire components. Span-to-span linking depends on a mechanism for specifying substructure within components. But in order to preserve the boundary between the hypertext network per se and the content/structure within the components, this mechanism cannot depend in any way on knowledge about the internal structure of (atomic) components. In the Dexter model, this is accomplished by an indirect addressing entity called an anchor. An anchor has two parts: an anchor id and an anchor value. The anchor value is an arbitrary value that specifies some location, region, item, or substructure within a component. This anchor value is interpretable only by the applications responsible for handling the content/structure of the component. It is primitive and unrestricted from the viewpoint of the storage layer. The anchor id is an identifier which uniquely identifies its anchor within the scope of its component. Anchors can therefore be uniquely identified across the whole universe by a component UID, anchor id pair.",{"_35":870,"_37":5792,"_39":521,"_41":5793,"_66":5794,"_68":5795,"_70":69},"l_p2Cbz4",{"_273":323},[],"An Overview of the Model",{"_35":870,"_37":5797,"_39":521,"_41":5798,"_66":5799,"_68":874,"_70":69},"UDzBaw-E",{"_273":323},[],[279],"/records/the-dexter-hypertext-reference-model",{"_82":541},{},{"_37":518,"_95":53,"_54":5805,"_71":521,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,520],1772031973223,[149,518,521],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/the-dexter-hypertext-reference-model\",\"bafy2bzacecj6hopdys7isf3mhrk63bfjjl3ewaeww4sx5ainwe2x2xlopsh3i\"]",{"_110":5810,"_147":7376,"_150":7377},{"_112":5811,"_131":132,"_133":7375,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":5812,"_37":7373},{"_28":5813,"_71":547,"_72":53,"_73":7368,"_54":7369,"_76":556,"_78":7370,"_80":7371,"_84":7372,"_86":557,"_88":89},[5814,5831,5849,5874,5930,6246,6714,6843,6906],{"_31":5815,"_33":5816},[],{"_35":160,"_37":5817,"_39":557,"_41":5818,"_66":5819,"_68":5830,"_70":69},"PmY0GNpK",{},[5820,5824],{"_35":919,"_167":5821,"_169":5822,"_41":5823,"_70":69},[137],[3184],{},{"_35":204,"_167":5825,"_169":5826,"_41":5828,"_70":5829},[3527],[5827],188,{},"mailto:hcd}@ecs.soton.ac.uk","Dave E. Millard, Luc Moreau, Hugh C. Davis\nMultimedia Research Group\nDepartment of Electronics & Computer Science\nUniversity of Southampton\nSO17 1BJ, UK\n{dem97r, lavm, hcd}@ecs.soton.ac.uk",{"_31":5832,"_33":5833},[],{"_35":160,"_37":5834,"_39":557,"_41":5835,"_66":5836,"_68":5848,"_70":69},"HgIzGG4W",{},[5837,5841],{"_35":919,"_167":5838,"_169":5839,"_41":5840,"_70":69},[137],[1488],{},{"_35":204,"_167":5842,"_169":5844,"_41":5846,"_70":5847},[5843],89,[5845],111,{},"mailto:sre@ifs.uni-linz.ac.at","Siegfried Reich\nDepartment of Information Systems\nUniversity of Linz, 4040 Linz, Austria\nsre@ifs.uni-linz.ac.at",{"_31":5850,"_33":5869},[5851,5858],{"_31":5852,"_33":5853},[],{"_35":160,"_37":5854,"_39":557,"_41":5855,"_66":5856,"_68":5857,"_70":69},"vQZNzmfD",{},[],"The Open Hypermedia Systems community has been largely concerned with interoperability between hypertext systems which share the same paradigm. It has evolved a component-based framework for this purpose, in which specific but incompatible middleware components are designed for each hypertext domain, such as navigational hypertext, spatial hypertext or taxonomic hypertext. This paper investigates the common features of these domains and introduces FOHM, a Fundamental Open Hypertext Model, which defines a common data model and set of related operations that are applicable for all three domains. Using this layer the paper explores the possible semantics of linking between different hypertext domains, and shows that each can introduce features which benefit the other domains.",{"_31":5859,"_33":5860},[],{"_35":160,"_37":5861,"_39":557,"_41":5862,"_66":5863,"_68":5868,"_70":69},"G9CbE7pz",{},[5864],{"_35":166,"_167":5865,"_169":5866,"_41":5867,"_70":69},[137],[1476],{},"KEYWORDS: Component-based Open Hypermedia System (CB-OHS), Open Hypermedia Protocol (OHP), Hypertext Domains, Fundamental Open Hypermedia Model (FOHM), Interoperability.",{"_35":870,"_37":5870,"_39":557,"_41":5871,"_66":5872,"_68":5873,"_70":69},"yFIL9VmP",{"_273":323},[],"ABSTRACT",{"_31":5875,"_33":5925},[5876,5883,5890,5897,5904,5911,5918],{"_31":5877,"_33":5878},[],{"_35":160,"_37":5879,"_39":557,"_41":5880,"_66":5881,"_68":5882,"_70":69},"Ll905OgE",{},[],"At the First Open Hypertext Systems (OHS) Workshop held at Hypertext '94, Antoine Rizk proposed that the workshop should design a protocol for communication between hypertext client programs and link servers [30]. The motivation for his suggestion was that the OHS community was wasting much time re-implementing client programs and wrappers for existing third-party applications. The premise of his proposal was that there were many features that were common to all hypertext systems, and that if we could produce a simple protocol that all clients used, then we would have interoperability of clients, and we could concentrate on research into link services and hyperbases.",{"_31":5884,"_33":5885},[],{"_35":160,"_37":5886,"_39":557,"_41":5887,"_66":5888,"_68":5889,"_70":69},"C_Nz11m2",{},[],"This goal seemed reasonable, and in 1996, Davis et al. reported back to the second OHS workshop with a draft proposal for such a protocol [4][17]. This proposal leant heavily on the authors’ own experiences in designing Microcosm and Multicard, and it had a few unfilled sections that the authors hoped that the Workshop would help to fill. However, when viewed by a wider community the draft proposal was seen to have many limitations [1]. One of the main problems was that the original protocol dealt only in a quite specific model of point-to-point navigational hypertext, and had no way of dealing with co-operation, distribution, or other models of hypertext such as taxonomic hypertext [19], spatial hypertext [10] or features such as transclusions in Xanadu [14].",{"_31":5891,"_33":5892},[],{"_35":160,"_37":5893,"_39":557,"_41":5894,"_66":5895,"_68":5896,"_70":69},"Gz4DKuge",{},[],"As a result the community moved on from a straightforward client/server approach to a component-based approach [29]. In this architecture, component-based middleware is implemented for each hypertext domain and is responsible for mapping the specific structures required by the client into and out of the structures stored in an all-purpose back-end server. This model provides an extensible architecture where new hypertext domains can be added by defining a new interface for this domain, and implementing an appropriate client and middleware component. This is fully reported in Reich et al. [21] and has been the subject of demonstrations in recent hypertext conferences, where components and systems from different research labs have been seen to interoperate.",{"_31":5898,"_33":5899},[],{"_35":160,"_37":5900,"_39":557,"_41":5901,"_66":5902,"_68":5903,"_70":69},"MHrOYuxW",{},[],"Having designed an architecture which allows multiple hypertext domains to operate alongside each other within a single framework, the community has recently become interested in the possibility of interoperability between the different hypertext domains themselves.",{"_31":5905,"_33":5906},[],{"_35":160,"_37":5907,"_39":557,"_41":5908,"_66":5909,"_68":5910,"_70":69},"Kl5SoPD_",{},[],"There are two distinct sorts of inter-domain interoperability that one might imagine. Let us imagine that there are two workspaces, the first which is a traditional navigational hypertext workspace, and the second which is a spatial hypertext. If there were a link from a node in the first workspace to a node in the second workspace, what would be the semantics of following this link? The first and perhaps most obvious outcome would be that as the link was followed into the spatial workspace, a spatial browser would open from where the user could continue to browse. However, an interesting second possibility could be that the navigational browser could remain open, and could continue to attempt to interpret the spatial workspace as if it was a navigational workspace. It was this second interpretation of inter-domain interoperability [16], that engendered the research reported in this paper.",{"_31":5912,"_33":5913},[],{"_35":160,"_37":5914,"_39":557,"_41":5915,"_66":5916,"_68":5917,"_70":69},"_InL-0DV",{},[],"In order for one hypertext domain to be able to interpret a second hypertext domain as if it were the first, then, using the current architecture, each middleware component must be adapted so that it can translate structures in all other domains into its own domain, and this solution will exhibit quadratic growth with the number of domains that intend to interoperate. Alternatively, we could attempt to define a common storage layer which would be sufficiently generic that it could store the structures required by all current domains, and hopefully all future domains.",{"_31":5919,"_33":5920},[],{"_35":160,"_37":5921,"_39":557,"_41":5922,"_66":5923,"_68":5924,"_70":69},"xWUlYcwf",{},[],"In this paper we start by describing the characteristics, similarities and differences between three of the existing hypertext domains (navigational, spatial and taxonomic). We then describe FOHM, a fundamental open hypertext model, which identifies data and permitted operations in a client/server style architecture. A formal specification of these operations and data is presented. We demonstrate that this model is sufficient to represent all the structural abstractions and operations of these three domains. We make the conjecture that our model is general enough to support other types of domains. Although it is not formally possible in the generic case to define a mapping back from the storage layer to any other domain, we discuss ways in which we can attempt this mapping, and we conclude by discussing the consequences of achieving such mappings, and the advantages and disadvantages that domains can introduce to each other.",{"_35":870,"_37":5926,"_39":557,"_41":5927,"_66":5928,"_68":5929,"_70":69},"sb1n8929",{"_273":323},[],"INTRODUCTION",{"_31":5931,"_33":6241},[5932,5939,5955,5962,5979,6025,6112,6168],{"_31":5933,"_33":5934},[],{"_35":160,"_37":5935,"_39":557,"_41":5936,"_66":5937,"_68":5938,"_70":69},"0fwmE9ep",{},[],"The application of hypertext is often seen in navigating information spaces with the World Wide Web serving as a prominent example. However, there are many more hypertext domains, each with their own specific needs and requirements. These domains include spatial hypertext, argumentation support, taxonomic hypertext, hypermedia art, hypermedia literature and others (for an overview see Nürnberg, 1997 [15]).",{"_31":5940,"_33":5949},[5941],{"_31":5942,"_33":5943},[],{"_35":1875,"_37":5944,"_39":557,"_41":5945,"_66":5946,"_68":5947,"_70":5948},"9pCZEaUv",{"_273":323},[],"Figure 1: The OHP Node Link model","ipfs://bafkreigrbfdajuklkysv266g42kuohvwidgkk6b4zkx4xsfsviv24za3um",{"_35":160,"_37":5950,"_39":5951,"_41":5952,"_66":5953,"_68":5954,"_70":69},"AyN47W6_","bafy2bzaceczj5pkxhxdspkpve4rkqixvqqkb2gw6lvquka2wdrj74fcyowxaw",{"_273":323},[],"These hypertext domains and the systems supporting them rely on different conceptual models [27]. The ultimate overall objective common to all these conceptual models is to “understand” information spaces [24]. Different criteria for measuring this objective may apply, e.g. metrics borrowed from software engineering such as “cohesion” and “coherence” [9], and the cognitive requirements of these domains differ. However, the domains could still be used together.",{"_31":5956,"_33":5957},[],{"_35":160,"_37":5958,"_39":5951,"_41":5959,"_66":5960,"_68":5961,"_70":69},"1l65rGvP",{},[],"For example, users navigating the Web may on arrival at a “new server” start by having a spatial overview of pages (nodes) available (e.g., by using a graphical map) before navigating them. Equally, after having read a set of nodes in a navigation browser, they may want to use a taxonomic tool in order to reason about the set of nodes they have read. For example, to determine whose opinions academic papers represent.",{"_31":5963,"_33":5964},[],{"_35":160,"_37":5965,"_39":5951,"_41":5966,"_66":5967,"_68":5978,"_70":69},"6gn5G9xE",{},[5968],{"_35":166,"_167":5969,"_169":5973,"_41":5977,"_70":69},[5970,5971,5972],133,157,180,[5974,5975,5976],155,174,199,{},"In the following, we will briefly describe some of these domains and reflect on their specific properties. The domains described are navigational hypertext, spatial hypertext, and taxonomic hypertext.",{"_31":5980,"_33":6020},[5981,5988,5995,6008],{"_31":5982,"_33":5983},[],{"_35":160,"_37":5984,"_39":5951,"_41":5985,"_66":5986,"_68":5987,"_70":69},"z1YEyH06",{},[],"Navigational hypertext is concerned with partitioning information spaces into nodes and establishing relationships between them such that users can navigate them. The concept is simple but powerful and usable. Links store connections between “hotspots” in documents. By clicking on one hotspot the user navigates to the one at the other end of the link. It is probably the oldest conceptual model of hypertext and is already mentioned by the pioneers [2,6,13]. Modern Open Hypermedia Systems (OHSs) combine many features of early systems, keeping linking information separate from documents and allowing for more powerful link structures, for example bi-directional or n-ary links.",{"_31":5989,"_33":5990},[],{"_35":160,"_37":5991,"_39":5951,"_41":5992,"_66":5993,"_68":5994,"_70":69},"1YwpeXpJ",{},[],"The model that we present here follows closely the data model specified by the Open Hypermedia Systems Working Group (OHSWG) [21]. It is based firmly on the definition of several important objects that make up a link structure. Consider the two links shown in Figure 1.",{"_31":5996,"_33":5997},[],{"_35":160,"_37":5998,"_39":5951,"_41":5999,"_66":6000,"_68":6007,"_70":69},"3ArEXrQV",{},[6001],{"_35":166,"_167":6002,"_169":6004,"_41":6006,"_70":69},[6003],315,[6005],323,{},"In this diagram there are two node objects. These represent the system’s notion of a document or a file. Each node may have several anchors associated with it. These are objects that define a region inside the node to use as a hotspot (for example, there could be an anchor from word twelve to word seventeen). The endpoint objects bind an anchor to a particular link. As an anchor can be bound to several links (see anchor 2 in the Figure), the endpoint contains all the information that is relevant to this anchor in the context of one particular link.",{"_31":6009,"_33":6010},[],{"_35":160,"_37":6011,"_39":5951,"_41":6012,"_66":6013,"_68":6019,"_70":69},"bgImLFGK",{},[6014],{"_35":2026,"_167":6015,"_169":6016,"_41":6018,"_70":69},[208],[6017],129,{},"Operations applied to objects include creation and deletion primitives for all the objects in the system as well as a Follow Link function that returns a set of endpoints based on a single input endpoint parameter according to the underlying link structures.",{"_35":870,"_37":6021,"_39":5951,"_41":6022,"_66":6023,"_68":6024,"_70":69},"tyUvr8Af",{"_273":323},[],"The Navigational Domain",{"_31":6026,"_33":6107},[6027,6042,6057,6074,6086,6099],{"_31":6028,"_33":6029},[],{"_35":160,"_37":6030,"_39":5951,"_41":6031,"_66":6032,"_68":6041,"_70":69},"scvWAVyG",{},[6033],{"_35":166,"_167":6034,"_169":6037,"_41":6040,"_70":69},[6035,6036],399,412,[6038,6039],407,420,{},"This domain of hypertext is also referred to as “Information Analysis” [9] or “Information Triage” [11]. It emerged from activities like collecting, comprehending, or interpreting diverse sets of information and the need to support such activities. Thus, as opposed to navigational hypertext, what matters is the ability to create and move nodes freely. The key characteristic is to leave structure implicit and informal (at least as presented to the user) [10].",{"_31":6043,"_33":6044},[],{"_35":160,"_37":6045,"_39":5951,"_41":6046,"_66":6047,"_68":6056,"_70":69},"MB1jMZhI",{},[6048],{"_35":166,"_167":6049,"_169":6052,"_41":6055,"_70":69},[6050,6051],560,574,[6053,6054],564,578,{},"Relationships between nodes are simply expressed by their visual characteristics such as spatial proximity, color, or shape. This results in some interesting properties. If, for instance, a node is slightly misaligned with other nodes, then this might express an uncertainty about whether this node is actually part of this relationship. In other words, it expresses classification within relationships, where some nodes are “more” related than others. Spatial hypertext systems are therefore inherently flexible. Examples of spatial hypertext systems include VIKI [10] and CAOS [22].",{"_31":6058,"_33":6059},[],{"_35":160,"_37":6060,"_39":5951,"_41":6061,"_66":6062,"_68":6073,"_70":69},"BEHLbEQP",{},[6063],{"_35":166,"_167":6064,"_169":6068,"_41":6072,"_70":69},[6065,954,6066,6067],71,518,545,[6069,6070,6071,6051],76,296,523,{},"The following conceptual model therefore summarizes spatial hypertext. Nodes are visual symbols servicing as wrappers to documents, therefore they have characteristics such as color, location, and shape. Nodes can be aggregated (visually), thus building collections of related objects. Composites are the visual representations of these collections, they also have visual characteristics and therefore can also be aggregated into other composites, although this relationship may not be circular. These collections are typed, i.e., they may form lists, matrices, sets, stacks, etc. This affects their visual presentation but also acts as an organizational aid, adding both order and internal structure to the collections (e.g., one node may be placed before another, or the proximity of one node to another could reflect the strength of their association).",{"_31":6075,"_33":6076},[],{"_35":160,"_37":6077,"_39":5951,"_41":6078,"_66":6079,"_68":6085,"_70":69},"6qzROyHH",{},[6080],{"_35":166,"_167":6081,"_169":6082,"_41":6084,"_70":69},[3453,1709],[182,6083],229,{},"Any spatial system has to make all of these relationships explicit in the system so that queries can be made of the information and that visual information can be stored economically. To this end, many systems use spatial parsers to convert the implicit spatial relationships into explicit associations within the system. It is this parser that recognizes the way in which nodes have been laid down and decides on an appropriate structure to store the information such as a list or a set.",{"_31":6087,"_33":6088},[],{"_35":160,"_37":6089,"_39":5951,"_41":6090,"_66":6091,"_68":6098,"_70":69},"xq_kWYto",{},[6092],{"_35":166,"_167":6093,"_169":6095,"_41":6097,"_70":69},[6094],106,[6096],112,{},"Operations on objects include creation and deletion, adding and removing objects to composites and also a ‘zoom’ function that allows a user to zoom into a composite’s sub-components.",{"_31":6100,"_33":6101},[],{"_35":1875,"_37":6102,"_39":5951,"_41":6103,"_66":6104,"_68":6105,"_70":6106},"UB4hxOtG",{"_273":323},[],"Figure 2: Example Taxonomy","ipfs://bafkreihrmhg3ci7u35ytvcoj7tzdxamrrna5iknz2d26eekw2l7ws2udju",{"_35":870,"_37":6108,"_39":5951,"_41":6109,"_66":6110,"_68":6111,"_70":69},"apnwW6sQ",{"_273":323},[],"The Spatial Domain",{"_31":6113,"_33":6163},[6114,6121,6128,6135,6156],{"_31":6115,"_33":6116},[],{"_35":160,"_37":6117,"_39":5951,"_41":6118,"_66":6119,"_68":6120,"_70":69},"1bOTc-As",{},[],"Taxonomic hypertext applies hypertext concepts such as non-linear information access and individualized views to the domain of reasoning about taxonomies, e.g. in biology, linguistics and other application areas [19, 27, 28].",{"_31":6122,"_33":6123},[],{"_35":160,"_37":6124,"_39":5951,"_41":6125,"_66":6126,"_68":6127,"_70":69},"FbzO19R4",{},[],"For this kind of knowledge task a model based on set theory is used [27]. Users sort artifacts (the equivalent of nodes) into categories (sets) based on their characteristics. Different users may have different views of how the artifacts are partitioned. Taxonomic reasoning is the process of moving around the structure by crossing the boundaries between overlapping sets.",{"_31":6129,"_33":6130},[],{"_35":160,"_37":6131,"_39":5951,"_41":6132,"_66":6133,"_68":6134,"_70":69},"yQ1Mep8N",{},[],"Figure 2 gives an example of a Taxonomy. Here two people have categorized five artifacts. They both agree that all five lie within category one and that artifacts one and two also lie within sub-category two. However they disagree on how the remaining three artifacts should be split up. The first view (perspective one) says that artifacts four and five lie in category four while artifact three lies in category five. The second view (perspective two) agrees that artifact three should be in category five but thinks that artifacts four and five are different enough to be categorized separately (in categories six and seven respectively).",{"_31":6136,"_33":6151},[6137,6144],{"_31":6138,"_33":6139},[],{"_35":160,"_37":6140,"_39":5951,"_41":6141,"_66":6142,"_68":6143,"_70":69},"8xWySiR_",{},[],"Whenever a taxonomy splits via perspectives the same artifacts can be reached down each branch, it is merely their categorization that changes.",{"_31":6145,"_33":6146},[],{"_35":160,"_37":6147,"_39":5951,"_41":6148,"_66":6149,"_68":6150,"_70":69},"skOrhFTm",{},[],"All categories are single parented within a single taxonomy (i.e., an artifact may be in two categories only when each parent category is within a different taxonomy).",{"_35":160,"_37":6152,"_39":5951,"_41":6153,"_66":6154,"_68":6155,"_70":69},"8BUh7kzd",{"_273":2113},[],"There are two important rules that govern the shape of taxonomies.",{"_31":6157,"_33":6158},[],{"_35":160,"_37":6159,"_39":5951,"_41":6160,"_66":6161,"_68":6162,"_70":69},"R2W2DbgH",{},[],"Artifacts can be added to categories and also removed. Categories are organized hierarchically so categories may be added and removed as well. Categories cannot be circular, as this is semantically meaningless [27]. In addition some set like operations are also required so as to reason about multiple taxonomies, such as set union and intersection.",{"_35":870,"_37":6164,"_39":5951,"_41":6165,"_66":6166,"_68":6167,"_70":69},"XUyK2O3s",{"_273":323},[],"The Taxonomic Domain",{"_31":6169,"_33":6236},[6170,6218,6229],{"_31":6171,"_33":6206},[6172,6183,6195],{"_31":6173,"_33":6174},[],{"_35":160,"_37":6175,"_39":5951,"_41":6176,"_66":6177,"_68":6182,"_70":69},"houBMpnS",{},[6178],{"_35":166,"_167":6179,"_169":6180,"_41":6181,"_70":69},[3476],[998],{},"The navigational domain contains anchors that allow links to point into documents rather than be anchored on entire documents.",{"_31":6184,"_33":6185},[],{"_35":160,"_37":6186,"_39":5951,"_41":6187,"_66":6188,"_68":6194,"_70":69},"-Zagm0IS",{},[6189],{"_35":166,"_167":6190,"_169":6191,"_41":6193,"_70":69},[1573],[6192],46,{},"The spatial domain introduces typed structures (e.g., lists, sets, etc.) to the relationships.",{"_31":6196,"_33":6197},[],{"_35":160,"_37":6198,"_39":5951,"_41":6199,"_66":6200,"_68":6205,"_70":69},"caRbWtIX",{},[6201],{"_35":166,"_167":6202,"_169":6203,"_41":6204,"_70":69},[1573],[3261],{},"The taxonomic domain contains perspective objects that allow the relationship structures to diverge according to different views.",{"_35":160,"_37":6207,"_39":5951,"_41":6208,"_66":6209,"_68":6217,"_70":69},"A_p-vxLJ",{"_273":274},[6210],{"_35":166,"_167":6211,"_169":6213,"_41":6216,"_70":69},[5845,6212],197,[6214,6215],115,208,{},"There are a number of similarities between the different hypertext domains: in all domains, we find notions of data (node in navigational, visual in spatial, or artifact in taxonomic hypertext) or association (link in navigational, composite in spatial or category in taxonomic hypertext). On the other hand, there are features that only appear in a single specific hypertext domain:",{"_31":6219,"_33":6220},[],{"_35":160,"_37":6221,"_39":5951,"_41":6222,"_66":6223,"_68":6228,"_70":69},"QsrEJmth",{},[6224],{"_35":166,"_167":6225,"_169":6226,"_41":6227,"_70":69},[6094],[3339],{},"Other differences concern restricting the possible composite structures for various domains. For example, circularity is allowed in navigational hypertext but not in taxonomic or spatial. A more elaborate comparison of hypertext domains based on different features can be found in [15].",{"_31":6230,"_33":6231},[],{"_35":160,"_37":6232,"_39":5951,"_41":6233,"_66":6234,"_68":6235,"_70":69},"TqTFce8x",{},[],"In the following section we will introduce a formal model of these domains which we shall then use to explore the common ground between them.",{"_35":870,"_37":6237,"_39":5951,"_41":6238,"_66":6239,"_68":6240,"_70":69},"kQBHMlBb",{"_273":323},[],"Comparison of Domains",{"_35":870,"_37":6242,"_39":557,"_41":6243,"_66":6244,"_68":6245,"_70":69},"DwDAWDYT",{"_273":323},[],"HYPERTEXT DOMAINS",{"_31":6247,"_33":6709},[6248,6306,6365,6507,6592,6663],{"_31":6249,"_33":6301},[6250,6269,6281,6288],{"_31":6251,"_33":6252},[],{"_35":160,"_37":6253,"_39":5951,"_41":6254,"_66":6255,"_68":6268,"_70":69},"glTAzYLf",{},[6256],{"_35":166,"_167":6257,"_169":6262,"_41":6267,"_70":69},[6258,1904,6259,6260,6261],99,366,504,519,[5845,6263,6264,6265,6266],238,398,510,527,{},"There are numerous formal models of hypertexts, but they differ according to their motivation. The Dexter model [8] defines a common vocabulary and its meaning in order to talk about hypertext systems. The hypertext abstract machine (HAM) [3] is an architectural description of a general-purpose, transaction-based, multi-user server for a hypertext storage system. Furuta and Stotts’ Trellis model [7] is a formal specification of hypertexts based on petri nets. Hypertexts have also been formalized as graphs [25] or automata [12, 20].",{"_31":6270,"_33":6271},[],{"_35":160,"_37":6272,"_39":5951,"_41":6273,"_66":6274,"_68":6280,"_70":69},"1d02gLFT",{},[6275],{"_35":919,"_167":6276,"_169":6277,"_41":6279,"_70":69},[3409],[6278],110,{},"Several authors [12, 20, 23] have studied the dynamic properties of hypertexts in terms of reader’s experience, formalizing what readers see when they interact with a hypertext system.",{"_31":6282,"_33":6283},[],{"_35":160,"_37":6284,"_39":5951,"_41":6285,"_66":6286,"_68":6287,"_70":69},"utfSLmXP",{},[],"In this paper, our motivation is to make data structures and operations pertaining to them explicit, so that we can define a model that is common to the different hypertext domains and investigate interoperability.",{"_31":6289,"_33":6290},[],{"_35":160,"_37":6291,"_39":6292,"_41":6293,"_66":6294,"_68":6300,"_70":69},"5tB6i6dL","bafy2bzacebm7tcambnzaerkt3yy7e33wvap6gehwb6vwmjgzpstp5pausq6xy",{},[6295],{"_35":166,"_167":6296,"_169":6298,"_41":6299,"_70":69},[6297],163,[246],{},"Since both data and operations have to be formalized, we adopt the same approach as Moreau and Hall [12] for our formalization of a hypertext domain. We define an abstract machine characterizing the states of hypertext clients and servers. We define the client as the browser, or user interface, displaying documents, whereas the server maintains the documents and all hyperstructures in its hyperbase. Supported operations are modeled by transitions of the abstract machine, possibly changing the internal states of the client and the server. In a first instance, we do not make distribution explicit, and we consider only one server in the system.",{"_35":870,"_37":6302,"_39":5951,"_41":6303,"_66":6304,"_68":6305,"_70":69},"wnqL9tXZ",{"_273":323},[],"What is a Formalization of a Hypertext Domain?",{"_31":6307,"_33":6360},[6308,6326,6339,6346,6353],{"_31":6309,"_33":6310},[],{"_35":160,"_37":6311,"_39":6292,"_41":6312,"_66":6313,"_68":6325,"_70":69},"2f3g9jfl",{},[6314],{"_35":919,"_167":6315,"_169":6320,"_41":6324,"_70":69},[6316,6317,6318,6319],94,170,194,370,[6321,5972,6322,6323],105,220,375,{},"Let us consider the navigational domain. The first step in the formalization is to define the state space of the abstract machine. The state space not only comprises the data model but also the architectural organization. The data model defines the different data that can be encountered: node, anchor, endpoint and link. The architectural organization is composed of a store containing all hyperstructures and the state of the client, which is the currently displayed document. Multiple windows, history lists, etc. are also possible to model but are beyond the scope of this work.",{"_31":6327,"_33":6328},[],{"_35":160,"_37":6329,"_39":6292,"_41":6330,"_66":6331,"_68":6338,"_70":69},"ANUIIrqz",{},[6332],{"_35":919,"_167":6333,"_169":6335,"_41":6337,"_70":69},[6334],54,[6336],64,{},"The second step in the formalization is to define the operations that may be performed: they include creating links (or any other data), retrieving data from the store, or even performing a query such as getting endpoints for a given data.",{"_31":6340,"_33":6341},[],{"_35":160,"_37":6342,"_39":6292,"_41":6343,"_66":6344,"_68":6345,"_70":69},"Fw3JfgHh",{},[],"Given a state S1NS_1^NS1N of the navigational abstract machine, executing an operation leads to a new state S2NS_2^NS2N, which we note as:",{"_31":6347,"_33":6348},[],{"_35":1875,"_37":6349,"_39":6292,"_41":6350,"_66":6351,"_68":69,"_70":6352},"rmOSN4ws",{"_273":323},[],"ipfs://bafkreig7tchth5bkiiakexfvetrezmjsw3zvb23n2qckbwjya7fymrdske",{"_31":6354,"_33":6355},[],{"_35":160,"_37":6356,"_39":6292,"_41":6357,"_66":6358,"_68":6359,"_70":69},"CC3XJSwg",{},[],"where ↦N denotes a transition following an operation in the navigational domain. Each hypertext domain may be formalized in a similar manner, which gives us transition relations ↦S for spatial hypertext and ↦T for taxonomic hypertext.",{"_35":870,"_37":6361,"_39":6292,"_41":6362,"_66":6363,"_68":6364,"_70":69},"URWN2VkW",{"_273":323},[],"Abstract Machine Transition",{"_31":6366,"_33":6502},[6367,6386,6418,6426,6440,6453,6467,6490],{"_31":6368,"_33":6369},[],{"_35":160,"_37":6370,"_39":6292,"_41":6371,"_66":6372,"_68":6385,"_70":69},"xukLwHtc",{},[6373,6380],{"_35":919,"_167":6374,"_169":6376,"_41":6379,"_70":69},[6065,6375],234,[6377,6378],88,266,{},{"_35":166,"_167":6381,"_169":6383,"_41":6384,"_70":69},[6382],282,[954],{},"Given the similarities between the different domains we have defined a fundamental layer as composed of data structures that are general enough to “encode” any data structure of each hypertext domain. These operations and data form a fundamental open hypertext model, which we call FOHM. We also define general operations on these data structures. Figure 3 contains the data model, whereas Figure 4 displays some operations on these data, which we now describe.",{"_31":6387,"_33":6388},[],{"_35":160,"_37":6389,"_39":6292,"_41":6390,"_66":6391,"_68":6417,"_70":69},"45s4fQIC",{},[6392,6402],{"_35":166,"_167":6393,"_169":6397,"_41":6401,"_70":69},[1464,6394,6395,6396],329,471,620,[1011,6398,6399,6400],341,478,638,{},{"_35":2026,"_167":6403,"_169":6409,"_41":6416,"_70":69},[2660,6404,3339,6405,6406,6407,1917,6408],108,141,305,425,466,[2531,6278,6410,6411,6412,6413,6414,6415],119,143,306,426,444,467,{},"The set of identifiers I is formed by the union of three sets of identifiers, respectively for associations Ia, data Id, and data references Ir (abbreviated refs). Data, typically documents, are not formalized in the hypertext layer; however, as we need to refer to them, we assume the existence of a set D of Data. The set A of associations is defined by the cartesian product of three sets, respectively of binding vectors B, relation types T and structural types S. A binding is composed of a ref ID and a vector of features; the former is meant to be the identifier of a reference, which “attaches” on a document. A vector of features can be regarded as an ordered set of properties, where each property identifies a value in a set of features, such as direction of a binding, geometric property, etc. ",{"_31":6419,"_33":6420},[],{"_35":1875,"_37":6421,"_39":5951,"_41":6422,"_66":6423,"_68":6424,"_70":6425},"PJ3svp4D",{"_273":323},[],"Figure 3: The Fundamental Data Model","ipfs://bafkreigfx7lichr6aeweow23ht3wkfblokms5e6p4ge3aeog5azvxjnig4",{"_31":6427,"_33":6428},[],{"_35":160,"_37":6429,"_39":6292,"_41":6430,"_66":6431,"_68":6439,"_70":69},"GuheTwVb",{},[6432],{"_35":166,"_167":6433,"_169":6435,"_41":6438,"_70":69},[2070,6434],431,[6436,6437],193,448,{},"By construction, we require the vector of features of all the bindings in a given association to have the same dimension as the feature space vector in the association. The feature space vector enumerates, by name, the different properties that must be defined in each binding of an association: this allows clients to construct bindings that are understood by servers and other clients. We can regard the vector of features as an extensible record, whose components are identified by the feature space vector. The extensible record is a critical technique to support other hypertext domains, as it allows us to implement data structures with a variable number of features. Finally, an association is also characterized by a structural type, such as heap, list, or stack, which exhibit different behaviors when the association is traversed.",{"_31":6441,"_33":6442},[],{"_35":160,"_37":6443,"_39":6292,"_41":6444,"_66":6445,"_68":6452,"_70":69},"QCGlX0IE",{},[6446],{"_35":166,"_167":6447,"_169":6449,"_41":6451,"_70":69},[6448,185],18,[2531,6450],79,{},"We define the set Object as the union of Data, Associations and Refs. The store, which is defined as the permanent memory of a server, maps identifiers onto objects.",{"_31":6454,"_33":6455},[],{"_35":160,"_37":6456,"_39":6292,"_41":6457,"_66":6458,"_68":6466,"_70":69},"huXm8jdb",{},[6459],{"_35":2026,"_167":6460,"_169":6462,"_41":6465,"_70":69},[1892,6461],474,[6463,6464],104,497,{},"Figure 4 displays some of the operations that are permitted on the data: for instance, createAssociation expects an association and a store, and if successful, returns a new identifier for the association, and an updated store, containing a mapping between the identifier and the association. As a result, retrieving an object associated with a valid identifier is performed by applying the store to the identifier. Along the same lines, adding a binding to an association (addBindingToAssociation) consists of retrieving the association and storing a new association with a new binding in the binding vector.",{"_31":6468,"_33":6469},[],{"_35":160,"_37":6470,"_39":6292,"_41":6471,"_66":6472,"_68":6489,"_70":69},"1jjW3ZWu",{},[6473,6483],{"_35":166,"_167":6474,"_169":6478,"_41":6482,"_70":69},[6475,6476,6477,1704],60,154,442,[6479,6480,1917,6481],70,161,493,{},{"_35":2026,"_167":6484,"_169":6486,"_41":6488,"_70":69},[6485],379,[6487],396,{},"Note that the specification of all functions in Figure 4 is executable. There are however operations whose specification is not executable, which we call queries. The specification constrains the type of results such queries should produce, but it does not indicate how the result should be obtained because we do not want to preclude any implementation. For instance, the query getBindingForData returns bindings with a given feature vector f and whose Data Ref refers to a given identifier i.",{"_31":6491,"_33":6492},[],{"_35":160,"_37":6493,"_39":6292,"_41":6494,"_66":6495,"_68":6501,"_70":69},"YWmOjwI_",{},[6496],{"_35":166,"_167":6497,"_169":6498,"_41":6500,"_70":69},[2280],[6499],405,{},"It is possible to formalize a complete abstract machine, composed of a client executing a sequence of operations and a server containing a store. Transitions will be defined in terms of the supported operations, and their effect on the client and server is defined using the definitions of Figure 4. As a result, we can define a transition relation for the fundamental hypertext machine, which we note ↦ F.",{"_35":870,"_37":6503,"_39":6292,"_41":6504,"_66":6505,"_68":6506,"_70":69},"0dkHrLxX",{"_273":323},[],"A Fundamental Hypertext Layer",{"_31":6508,"_33":6587},[6509,6521,6537,6546,6552,6559,6566,6573,6580],{"_31":6510,"_33":6511},[],{"_35":160,"_37":6512,"_39":6292,"_41":6513,"_66":6514,"_68":6520,"_70":69},"wJt0oxuo",{},[6515],{"_35":166,"_167":6516,"_169":6518,"_41":6519,"_70":69},[6517],177,[5827],{},"The claim that the fundamental layer is general enough to encode any of our three selected hypertext domains may itself be formalized. For each hypertext domain, there exists a translation that converts any state of the abstract machine into a configuration of the fundamental hypertext abstract machine. Similarly, for each hypertext domain, each transition of the abstract machine may be translated into one (or more) transition(s) of the fundamental hypertext abstract machine.",{"_31":6522,"_33":6523},[],{"_35":160,"_37":6524,"_39":6292,"_41":6525,"_66":6526,"_68":6536,"_70":69},"ZfYk5iyi",{},[6527],{"_35":166,"_167":6528,"_169":6531,"_41":6535,"_70":69},[6529,6530,3339],63,98,[6532,6533,6534],65,100,123,{},"For the navigational domain, the translation function is noted Tₙ, and given a navigational state Sₙ, the expression Tₙ⟦Sₙ⟧ denotes the corresponding fundamental state.",{"_31":6538,"_33":6539},[],{"_35":1875,"_37":6540,"_39":6541,"_41":6542,"_66":6543,"_68":6544,"_70":6545},"FT_KPXXE","bafy2bzacec24kj53njhajtetvwk62g7uef453m5eor4h3d7himepsavah3ynu",{"_273":323},[],"Figure 4: Some Fundamental Functions and Queries","ipfs://bafkreiame35p55pgzxp74zmenseafiarqa7kusqmnt3rnyukvcaudwtha4",{"_31":6547,"_33":6548},[],{"_35":160,"_37":6549,"_39":6292,"_41":6550,"_66":6551,"_68":69,"_70":69},"egKqh40U",{},[],{"_31":6553,"_33":6554},[],{"_35":160,"_37":6555,"_39":6541,"_41":6556,"_66":6557,"_68":6558,"_70":69},"GIXT4KGc",{},[],"endpoint is mapped onto a binding whose feature vector contains a single entry whose value is in the set Dir. ii) A composite of the spatial domain is defined by an association with a three dimensional vector space for shape, color and location. There is no direct equivalent of a binding in the spa- tial domain, however, the translation creates such a binding, with a feature vector containing the shape, color and location of the data in the composite.",{"_31":6560,"_33":6561},[],{"_35":160,"_37":6562,"_39":6541,"_41":6563,"_66":6564,"_68":6565,"_70":69},"smr6Mfhy",{},[],"There is a strong relationship between the transition relations that we defined for each hypertext domain and the translation to the fundamental layer. It takes the form of a diamond prop- erty property, which we can state as follows. Let S₁ᴺ, S₂ᴺ be two states of the navigational domain and S₁ᶠ a state of the fundamental one. If there is a translation from S₁ᴺ to S₁ᶠ, and if there is a transition from S₁ᴺ to S₂ᴺ, then there exists S₂ᶠ, such that there is one (or more) transitions from S₁ᶠ to S₂ᶠ, and S₂ᶠ is the result of the translation of S₂ᴺ into the fundamental layer. Such a property is summarized by the following commutative diagram:",{"_31":6567,"_33":6568},[],{"_35":2026,"_37":6569,"_39":6541,"_41":6570,"_66":6571,"_68":6572,"_70":69},"VEbEg7qc",{"_2029":69},[]," S₁ᴺ ⟶ᴺ S₂ᴺ \n ↓ Tᴺ ↓ Tᴺ \n S₁ᶠ ⟶⁺ᶠ S₂ᶠ ",{"_31":6574,"_33":6575},[],{"_35":160,"_37":6576,"_39":6541,"_41":6577,"_66":6578,"_68":6579,"_70":69},"M44ka8ZH",{},[],"Similar properties also hold for the spatial and taxonomic hypertexts.",{"_31":6581,"_33":6582},[],{"_35":160,"_37":6583,"_39":6541,"_41":6584,"_66":6585,"_68":6586,"_70":69},"Odt2tt7H",{},[],"Intuitively, this property states that the fundamental layer is expressive enough to encode any of the three hypertext do- mains and simulate its behavior. We make the conjecture that our model is general enough to simulate other hypertext domains: in particular, extensible records can accommodate features that are not present in the three investigated domains.",{"_35":870,"_37":6588,"_39":6541,"_41":6589,"_66":6590,"_68":6591,"_70":69},"fCl0c2HK",{"_273":323},[],"A Translation to the Fundamental Hypertext Layer",{"_31":6593,"_33":6658},[6594,6602,6609,6616,6623,6630,6651],{"_31":6595,"_33":6596},[],{"_35":160,"_37":6597,"_39":6598,"_41":6599,"_66":6600,"_68":6601,"_70":69},"LOu_flo7","bafy2bzaceagvsgsvcpq7i2sxmlhoisk325ax4m3kj4rowt6gdvdsoi62abr3e",{},[],"Interestingly, each translation to the fundamental layer is reversible. Let us call Tᴺ⁻¹ the inverse translation of Tᴺ. The following property holds: for any state Sᴺ of the navigational hypertext machine,",{"_31":6603,"_33":6604},[],{"_35":2026,"_37":6605,"_39":6541,"_41":6606,"_66":6607,"_68":6608,"_70":69},"EZv_LUNR",{"_2029":69},[]," Tᴺ⁻¹[Tᴺ[Sᴺ]] = Sᴺ.",{"_31":6610,"_33":6611},[],{"_35":160,"_37":6612,"_39":6598,"_41":6613,"_66":6614,"_68":6615,"_70":69},"LN7KQTmU",{},[],"A similar property holds for the other translations from spatial and taxonomic. Consequently, the above commutative diagram may be rewritten as follows.",{"_31":6617,"_33":6618},[],{"_35":2026,"_37":6619,"_39":6598,"_41":6620,"_66":6621,"_68":6622,"_70":69},"EkijFwzi",{"_2029":69},[]," S₁ᴺ ⟶ᴺ S₂ᴺ \n ↓ Tᴺ ↑ Tᴺ⁻¹ \n S₁ᶠ ⟶⁺ᶠ S₂ᶠ \n",{"_31":6624,"_33":6625},[],{"_35":160,"_37":6626,"_39":6598,"_41":6627,"_66":6628,"_68":6629,"_70":69},"gfMpXSz7",{},[],"This diagram proves that the fundamental layer can be used to implement any hypertext domain. Given a state, it suffices to convert it to the fundamental representation, to perform the operation in the fundamental layer, and to convert the state back to the initial domain.",{"_31":6631,"_33":6646},[6632,6639],{"_31":6633,"_33":6634},[],{"_35":160,"_37":6635,"_39":6598,"_41":6636,"_66":6637,"_68":6638,"_70":69},"gX8ZMiyh",{},[],"behaviors of any domain can be explained in terms of the fundamental layer,",{"_31":6640,"_33":6641},[],{"_35":160,"_37":6642,"_39":6598,"_41":6643,"_66":6644,"_68":6645,"_70":69},"hqRE_-ED",{},[],"execution in the fundamental layer suffices, and domain specific information has to be converted only when made visible to the user:",{"_35":160,"_37":6647,"_39":6598,"_41":6648,"_66":6649,"_68":6650,"_70":69},"lfx2zSLa",{"_273":2113},[],"Note that we do not recommend that any hypertext is implemented by this complex double translation; however, this result shows that:",{"_31":6652,"_33":6653},[],{"_35":2026,"_37":6654,"_39":6598,"_41":6655,"_66":6656,"_68":6657,"_70":69},"mstDjIwy",{"_2029":69},[]," S₁ᴺ ⟶ᴺ S₂ᴺ \n ↑ Tᴺ⁻¹ ↑ Tᴺ⁻¹ \n S₁ᶠ ⟶⁺ᶠ S₂ᶠ ",{"_35":870,"_37":6659,"_39":6598,"_41":6660,"_66":6661,"_68":6662,"_70":69},"QVUQi-7B",{"_273":323},[],"A Fundamental Implementation Technique",{"_31":6664,"_33":6704},[6665,6678,6685,6692],{"_31":6666,"_33":6667},[],{"_35":160,"_37":6668,"_39":6598,"_41":6669,"_66":6670,"_68":6677,"_70":69},"B-uOOpS3",{},[6671],{"_35":2026,"_167":6672,"_169":6673,"_41":6676,"_70":69},[3476,6258,1032],[6674,5591,6675],52,147,{},"Note that the symmetric property Tᴺ[[Tᴺ⁻¹[Sᶠ]]] = Sᶠ does not hold because the inverse translation Tᴺ⁻¹ is not defined for any fundamental state Sᶠ. However, the inverse translation is the route to interoperability between hypertext domains.",{"_31":6679,"_33":6680},[],{"_35":160,"_37":6681,"_39":6598,"_41":6682,"_66":6683,"_68":6684,"_70":69},"SkkPSbTJ",{},[],"Inverse translations may be extended to support data that come from different domains. It then becomes possible to define the meaning of domain-specific operations on data that do not belong to that domain. For instance, mapping a navigational hypertext to spatial hypertext is defined as follows:",{"_31":6686,"_33":6687},[],{"_35":2026,"_37":6688,"_39":6598,"_41":6689,"_66":6690,"_68":6691,"_70":69},"LHr5tBOS",{"_2029":69},[],"Tₛ⁻¹[[Tᴺ[[Sᴺ]]]]",{"_31":6693,"_33":6694},[],{"_35":160,"_37":6695,"_39":6598,"_41":6696,"_66":6697,"_68":6703,"_70":69},"C3S9DJQV",{},[6698],{"_35":2026,"_167":6699,"_169":6700,"_41":6702,"_70":69},[2660],[6701],27,{},"but requires extending Tₛ⁻¹ to objects of the navigational domain.",{"_35":870,"_37":6705,"_39":6598,"_41":6706,"_66":6707,"_68":6708,"_70":69},"ajId56Ba",{"_273":323},[],"Investigating Interoperability",{"_35":870,"_37":6710,"_39":5951,"_41":6711,"_66":6712,"_68":6713,"_70":69},"bIDw6ZOu",{"_273":323},[],"FORMALIZATION",{"_31":6715,"_33":6838},[6716,6723,6745,6787,6795,6803,6810],{"_31":6717,"_33":6718},[],{"_35":160,"_37":6719,"_39":6598,"_41":6720,"_66":6721,"_68":6722,"_70":69},"Anp_4xXH",{},[],"We have already stated that there are several features that only appear in any one of the three domains. The key to creating an inverse translation is to define corresponding features in the other two domains. These features should not be arbitrary but meaningful; bringing something to the domain that was not previously present. In this section, we suggest cross-domain translations of data-structures and their consequences.",{"_31":6724,"_33":6740},[6725,6732],{"_31":6726,"_33":6727},[],{"_35":160,"_37":6728,"_39":6598,"_41":6729,"_66":6730,"_68":6731,"_70":69},"yrpDNOay",{},[],"Anchors allow navigational clients to reference parts of documents that they would otherwise have to refer to in their entirety. This is particularly useful when defining hotspots but can also be useful when defining destination points, particularly in large documents or temporal media. The notion of an anchor could easily be extended to the other domains. Allowing parts of larger documents to be organized spatially or taxonomically and improving the granularity of referencing.",{"_31":6733,"_33":6734},[],{"_35":1875,"_37":6735,"_39":6598,"_41":6736,"_66":6737,"_68":6738,"_70":6739},"sZFDldNA",{"_273":323},[],"Figure 5: Link Structures","ipfs://bafkreicw47opvk66dwkfjdtticnjhk7xv23mjbr4vsehag6qdatgjuefay",{"_35":870,"_37":6741,"_39":6598,"_41":6742,"_66":6743,"_68":6744,"_70":69},"uaTv1qmv",{"_273":323},[],"Navigational Anchors",{"_31":6746,"_33":6782},[6747,6754,6761,6768,6775],{"_31":6748,"_33":6749},[],{"_35":160,"_37":6750,"_39":6598,"_41":6751,"_66":6752,"_68":6753,"_70":69},"a9Q95ftL",{},[],"Spatial structures are different from other associations in that they contain internal structure. This provides the ability to produce sequences of nodes (using queues, lists and stacks) as well as maps that provide information about the distance of one link endpoint from another (through the use of matrixes). In taxonomic hypertext this would become another distinguishing feature of a category, allowing perspectives to split over structure as well as content. In navigation it could provide more structured movement through the information space. Navigational hypertext involves associations in two ways: traversal and arrival and each would be effected by internal structure.",{"_31":6755,"_33":6756},[],{"_35":160,"_37":6757,"_39":6598,"_41":6758,"_66":6759,"_68":6760,"_70":69},"OokOROJ3",{},[],"Traversal is the act of following a link [26]. At the moment a link is effectively a set, if it could have different internal structure then the behavior of the traversal could vary according to that structure. Arrival is the act of viewing a structure (for example at the end of a traversal). Here internal structure could effect the way in which members of the association are viewed. Table 1 shows some possible semantics for traversal and arrival over different structures.",{"_31":6762,"_33":6763},[],{"_35":160,"_37":6764,"_39":6598,"_41":6765,"_66":6766,"_68":6767,"_70":69},"igeRUQqe",{},[],"These structural types would add valuable organization to otherwise disorganized hyperwebs. For example take a look at Figure 5.",{"_31":6769,"_33":6770},[],{"_35":160,"_37":6771,"_39":6598,"_41":6772,"_66":6773,"_68":6774,"_70":69},"5Jm5TnTf",{},[],"In Figure 5, the left hand link is represented as a Set, this means it is unordered but that no endpoint (A, B, C, D and E respectively) appears more then once. The right hand link is represented as a Stack; similar to a Set except it contains some internal structure, such that endpoint A is on the top of the stack while endpoint D is on the bottom. Our link semantics dictate that when users arrive at a Set they see all of the endpoints contained, thus if users arrive at the left hand link they see all the endpoints A through E. However, when they arrive at a Stack they see only the top endpoint of the stack, so in the case of the right hand link, this means they see endpoint A.",{"_31":6776,"_33":6777},[],{"_35":160,"_37":6778,"_39":6598,"_41":6779,"_66":6780,"_68":6781,"_70":69},"hEf2YK48",{},[],"When traversing a link the user always uses an endpoint that is a member of that link as a starting point. When traversing a Set the user arrives at all the endpoints except the starting one. So if the user started from endpoint B on the left hand...",{"_35":870,"_37":6783,"_39":6598,"_41":6784,"_66":6785,"_68":6786,"_70":69},"LksjSwDA",{"_273":323},[],"Spatial Structures",{"_31":6788,"_33":6789},[],{"_35":1875,"_37":6790,"_39":6598,"_41":6791,"_66":6792,"_68":6793,"_70":6794},"8RYyvPaH",{"_273":323},[],"Table 1: Semantics of Traversal and Arrival","ipfs://bafkreiceuhuiti57awh3bcdp5sk2k5h76eiyqll3fkaiumug44fjxvezom",{"_31":6796,"_33":6797},[],{"_35":1875,"_37":6798,"_39":6598,"_41":6799,"_66":6800,"_68":6801,"_70":6802},"tygrC2gm",{"_273":323},[],"Figure 6: A Perspective over two Nodes","ipfs://bafkreidpg6ldyidkz63j5pveifdnh2pngq67m3okie54kcebu43etanoyy",{"_31":6804,"_33":6805},[],{"_35":160,"_37":6806,"_39":6598,"_41":6807,"_66":6808,"_68":6809,"_70":69},"EanKWN17",{},[],"link then they would arrive at endpoints A, C, D and E. However, when a user traverses a stack they arrive at the endpoints to either side of their starting point. So if they started from endpoint B on the right hand link then they would arrive only at endpoints A and C.",{"_31":6811,"_33":6833},[6812,6819,6826],{"_31":6813,"_33":6814},[],{"_35":160,"_37":6815,"_39":6598,"_41":6816,"_66":6817,"_68":6818,"_70":69},"gqED_tf3",{},[],"Taxonomic perspectives allow different views of the organizations of some set of nodes within a branch of a hierarchy. Perspective is an abstraction that is in many ways similar to that of “context” as used in some navigational hypertext systems. Although a definition of context is beyond the scope of this paper (for an overview see [5]), it is generally understood that data (nodes and links etc.) will be arranged in a number of different contexts, and that the arrangement that will be seen by a user will depend in some way on a model that is known about this user, for example, what they have seen before, or their skill level.",{"_31":6820,"_33":6821},[],{"_35":160,"_37":6822,"_39":6598,"_41":6823,"_66":6824,"_68":6825,"_70":69},"6Uk28cpw",{},[],"Modeling perspectives as associations has the interesting property of allowing users to move between the different views just as if you were following a link. It also provides a convenient way of choosing a view. For example, in Figure 6, arriving by link 2 takes you directly into a particular view, whereas arriving by link 1 takes you to the perspective itself, where the system (or the user) can decide which view to provide. These are very much the properties that are required by context in other hypertext systems.",{"_31":6827,"_33":6828},[],{"_35":160,"_37":6829,"_39":6598,"_41":6830,"_66":6831,"_68":6832,"_70":69},"FjsEhPNc",{},[],"FOHM does not currently have any model of context, but these observations indicate the need for this extension, and demonstrate the way in which the features of one domain can add to and improve the features in another.",{"_35":870,"_37":6834,"_39":6598,"_41":6835,"_66":6836,"_68":6837,"_70":69},"CyQKTsGQ",{"_273":323},[],"Taxonomic Perspectives",{"_35":870,"_37":6839,"_39":6598,"_41":6840,"_66":6841,"_68":6842,"_70":69},"V8exs9wm",{"_273":323},[],"INTEROPERABILITY BETWEEN DOMAINS",{"_31":6844,"_33":6901},[6845,6852,6859,6866,6873,6880,6887,6894],{"_31":6846,"_33":6847},[],{"_35":160,"_37":6848,"_39":6598,"_41":6849,"_66":6850,"_68":6851,"_70":69},"NmY6-KkC",{},[],"Inter-domain interoperability is a relatively new concern to the hypermedia community. This paper has presented one solution involving the definition of FOHM, a common model capable of representing structures and implementing operations from any of the three domains presented. Thanks to our use of extensible records, we make the conjecture that FOHM is general enough to support other hypertext domains.",{"_31":6853,"_33":6854},[],{"_35":160,"_37":6855,"_39":6598,"_41":6856,"_66":6857,"_68":6858,"_70":69},"SoNsfJ6P",{},[],"This is somewhat in contrast to [21] where a dynamic arrangement of middleware components (known as structure servers) are responsible for dealing with the differing semantics of various domains stored in a storage layer. The advantage of this is that the system is able to cope with a wide range of different domains and adapt to the introduction of new ones. However, because it is not known which structure servers will be built on top of the storage layer the interface between the two has to be very general and system performance can suffer as a result. FOHM avoids these problems because it restricts itself to three common domains and is therefore able to “know” about certain fundamental properties (such as structure type). An additional advantage is that frontend entities serving one domain (e.g. navigational hypertext) are to a certain extent able to reason about other domains (e.g. spatial hypertext).",{"_31":6860,"_33":6861},[],{"_35":160,"_37":6862,"_39":6598,"_41":6863,"_66":6864,"_68":6865,"_70":69},"SK8qn9fs",{},[],"In particular FOHM captures the hypertext structure of the various domains so that middleware components become optional rather than a necessity and clients inherit the responsibility of fulfilling structural requirements. For example a link created in a navigational client would need to be interpreted as a set by a spatial browser. In FOHM no interpretation is needed as the concept of association structure (lists, sets etc.) is captured in the model. In other words both navigational and spatial browsers know about sets and therefore the navigational client would already have added this itself.",{"_31":6867,"_33":6868},[],{"_35":160,"_37":6869,"_39":6598,"_41":6870,"_66":6871,"_68":6872,"_70":69},"uZjFeDuj",{},[],"Non-critical information that has not been captured in the model could still be dealt with by middleware. Presentation information, such as color, is a particularly good example. In this case it is the responsibility of either the client or the server to use sensible defaults to fill in information that it requires but that is not stipulated in the model. Such information is dependent on that particular client or server (for example a client that displays only greyscale) and has no place in the model presented here.",{"_31":6874,"_33":6875},[],{"_35":160,"_37":6876,"_39":6598,"_41":6877,"_66":6878,"_68":6879,"_70":69},"4Rk-49yw",{},[],"We have also shown that the exercise of defining a common model for these selected hypertext domains potentially results in a type of “cross fertilization” in that domains may benefit from each other. For instance, structure types as required in spatial hypertext may well be applied to navigation or taxonomic hypertext as well. Equally, perspectives as known from taxonomic hypertext contribute to both the other domains. It is particularly interesting to note that the functionality added seems to reflect many of the features previously worked into hypermedia systems. For example perspectives seem to reflect the need for context and when viewed in a navigational browser lists appear to be very similar to the notion of a tour or a trail.",{"_31":6881,"_33":6882},[],{"_35":160,"_37":6883,"_39":6598,"_41":6884,"_66":6885,"_68":6886,"_70":69},"pDgLgLZb",{},[],"We believe that the fact that FOHM reflects these requirements is very encouraging and intend to extend the formal definition to include the inverse mappings described. In addition a comprehensive set of structural types needs to be decided and the semantics of link traversal and arrival on these structures defined.",{"_31":6888,"_33":6889},[],{"_35":160,"_37":6890,"_39":6598,"_41":6891,"_66":6892,"_68":6893,"_70":69},"30QmMO8y",{},[],"As a practical proof of concept a navigational and a spatial browser have been implemented, both of which use the FOHM server. It is envisaged that a taxonomic browser will also be written with the intention of exploring the quality and validity of macro-structures (such as a whole taxonomic hierarchy) that have been through a map-inverse map process.",{"_31":6895,"_33":6896},[],{"_35":160,"_37":6897,"_39":6598,"_41":6898,"_66":6899,"_68":6900,"_70":69},"TlqkzBh0",{},[],"The potential of FOHM to be included in the component based approach also needs to be evaluated. For example it could build a basis for a structural computing environment [18]. The model forms a layer that is both general enough to serve multiple domains and specific enough to allow the particular features of these domains to be expressed fully. Most importantly, by identifying the commonalities of the domains, it minimizes the performance cost normally associated with such a generic approach.",{"_35":870,"_37":6902,"_39":6598,"_41":6903,"_66":6904,"_68":6905,"_70":69},"8qRPX7bI",{"_273":323},[],"SUMMARY AND CONCLUSIONS",{"_31":6907,"_33":7363},[6908,6923,6938,6954,6973,6989,7000,7016,7032,7047,7063,7078,7093,7108,7119,7137,7153,7170,7185,7201,7218,7235,7251,7267,7282,7300,7316,7333,7348],{"_31":6909,"_33":6910},[],{"_35":160,"_37":6911,"_39":6598,"_41":6912,"_66":6913,"_68":6922,"_70":69},"sgEcn16H",{},[6914,6918],{"_35":166,"_167":6915,"_169":6916,"_41":6917,"_70":69},[137],[6674],{},{"_35":919,"_167":6919,"_169":6920,"_41":6921,"_70":69},[225],[1805],{},"Anderson, K. M., Taylor, R. N., and Whitehead, E. J. A critique of the open hypermedia protocol. Journal of Digital Information (JoDI). Special Issue on Open Hypermedia Systems 1, 2 (1997).",{"_31":6924,"_33":6925},[],{"_35":160,"_37":6926,"_39":6598,"_41":6927,"_66":6928,"_68":6937,"_70":69},"xHYuuq34",{},[6929,6933],{"_35":166,"_167":6930,"_169":6931,"_41":6932,"_70":69},[137],[240],{},{"_35":919,"_167":6934,"_169":6935,"_41":6936,"_70":69},[3363],[3545],{},"Bush, V. As we may think. The Atlantic Monthly 176, 1 (1945), 101–108.",{"_31":6939,"_33":6940},[],{"_35":160,"_37":6941,"_39":6598,"_41":6942,"_66":6943,"_68":6953,"_70":69},"SIYYqzQ7",{},[6944,6948],{"_35":166,"_167":6945,"_169":6946,"_41":6947,"_70":69},[137],[987],{},{"_35":919,"_167":6949,"_169":6951,"_41":6952,"_70":69},[6950],84,[6096],{},"Campbell, B., and Goodman, J. M. HAM: A General Purpose Hypertext Abstract Machine. Communications of the ACM 31, 7 (July 1988), 856–861.",{"_31":6955,"_33":6956},[],{"_35":160,"_37":6957,"_39":6598,"_41":6958,"_66":6959,"_68":6972,"_70":69},"Tp5QY08U",{},[6960,6964],{"_35":166,"_167":6961,"_169":6962,"_41":6963,"_70":69},[137],[998],{},{"_35":919,"_167":6965,"_169":6968,"_41":6971,"_70":69},[6966,6967,3126],107,204,[973,6969,6970],215,338,{},"Davis, H. C., Rizk, A., and Lewis, A. J. OHP: A draft proposal for a standard open hypermedia protocol. In Proceedings of the 2nd Workshop on Open Hypermedia Systems, ACM Hypertext ’96, Washington, D.C., March 16–20. Available as Report No. ICS-TR-96-10 from the Dept. of Information and Computer Science, University of California, Irvine (1996), U. K. Wiil and S. Demeyer, Eds., pp. 27–53.",{"_31":6974,"_33":6975},[],{"_35":160,"_37":6976,"_39":6598,"_41":6977,"_66":6978,"_68":6988,"_70":69},"oYlJLIw_",{},[6979,6984],{"_35":166,"_167":6980,"_169":6981,"_41":6983,"_70":69},[137],[6982],10,{},{"_35":919,"_167":6985,"_169":6986,"_41":6987,"_70":69},[6258],[6017],{},"Dervin, B. Given a context by any other name: Methodological tools for taming the unruly beast. In Information Seeking in Context (1997), Taylor Graham, London, pp. 13–38.",{"_31":6990,"_33":6991},[],{"_35":160,"_37":6992,"_39":6598,"_41":6993,"_66":6994,"_68":6999,"_70":69},"WRT7LqDn",{},[6995],{"_35":166,"_167":6996,"_169":6997,"_41":6998,"_70":69},[137],[1488],{},"Engelbart, D. C. Augmenting human intellect: A conceptual framework. Tech. Rep. AFOSR-3223, Contract AF 49(638)-1024, Stanford Research Institute Technical Report, Palo Alto, CA, Oct. 1962.",{"_31":7001,"_33":7002},[],{"_35":160,"_37":7003,"_39":6598,"_41":7004,"_66":7005,"_68":7015,"_70":69},"yvTQeBJF",{},[7006,7010],{"_35":166,"_167":7007,"_169":7008,"_41":7009,"_70":69},[137],[3407],{},{"_35":919,"_167":7011,"_169":7013,"_41":7014,"_70":69},[7012],77,[6463],{},"Furuta, R., and Stotts, P. D. Programmable Browsing Semantics in Trellis. In Proceedings of Hypertext’89 (Nov. 1989), pp. 27–42.",{"_31":7017,"_33":7018},[],{"_35":160,"_37":7019,"_39":6598,"_41":7020,"_66":7021,"_68":7031,"_70":69},"PjPt2vxQ",{},[7022,7026],{"_35":166,"_167":7023,"_169":7024,"_41":7025,"_70":69},[137],[3374],{},{"_35":919,"_167":7027,"_169":7029,"_41":7030,"_70":69},[7028],67,[921],{},"Halasz, F., and Schwartz, M. The dexter hypertext reference model. Communications of the ACM 37, 2 (1994), 30–39.",{"_31":7033,"_33":7034},[],{"_35":160,"_37":7035,"_39":6598,"_41":7036,"_66":7037,"_68":7046,"_70":69},"L_Zduggd",{},[7038,7042],{"_35":166,"_167":7039,"_169":7040,"_41":7041,"_70":69},[137],[1011],{},{"_35":919,"_167":7043,"_169":7044,"_41":7045,"_70":69},[2660],[5576],{},"Lowe, D., and Hall, W. Hypermedia & the Web. An Engineering Approach. John Wiley & Sons, Chichester, 1999.",{"_31":7048,"_33":7049},[],{"_35":160,"_37":7050,"_39":6598,"_41":7051,"_66":7052,"_68":7062,"_70":69},"KlZ4FrXI",{},[7053,7057],{"_35":166,"_167":7054,"_169":7055,"_41":7056,"_70":69},[137],[2261],{},{"_35":919,"_167":7058,"_169":7059,"_41":7061,"_70":69},[225],[7060],182,{},"Marshall, C. C., and Shipman, F. M. Spatial hypertext and the practice of information triage. In Proceedings of the ’97 ACM Conference on Hypertext, April 6-11, 1997, Southampton, UK (1997), pp. 124–133.",{"_31":7064,"_33":7065},[],{"_35":160,"_37":7066,"_39":6598,"_41":7067,"_66":7068,"_68":7077,"_70":69},"2wHbzY6K",{},[7069,7073],{"_35":166,"_167":7070,"_169":7071,"_41":7072,"_70":69},[137],[2531],{},{"_35":919,"_167":7074,"_169":7075,"_41":7076,"_70":69},[1543],[227],{},"Moreau, L., and Hall, W. On the Expressiveness of Links in Hypertext Systems. The Computer Journal 41, 7 (1998), 459–473.",{"_31":7079,"_33":7080},[],{"_35":160,"_37":7081,"_39":6598,"_41":7082,"_66":7083,"_68":7092,"_70":69},"U3Bh85-L",{},[7084,7088],{"_35":166,"_167":7085,"_169":7086,"_41":7087,"_70":69},[137],[1520],{},{"_35":919,"_167":7089,"_169":7090,"_41":7091,"_70":69},[1000],[1892],{},"Nelson, T. H. Getting it out of our system. In Information Retrieval: A Critical Review, G. Schechter, Ed. Thompson Books, Washington, D.C., 1967, pp. 191–210.",{"_31":7094,"_33":7095},[],{"_35":160,"_37":7096,"_39":6598,"_41":7097,"_66":7098,"_68":7107,"_70":69},"weCav6DK",{},[7099,7103],{"_35":166,"_167":7100,"_169":7101,"_41":7102,"_70":69},[137],[1520],{},{"_35":919,"_167":7104,"_169":7105,"_41":7106,"_70":69},[171],[987],{},"Nelson, T. H. Literary Machines. Published by the author. Mindful Press, 1987.",{"_31":7109,"_33":7110},[],{"_35":160,"_37":7111,"_39":6598,"_41":7112,"_66":7113,"_68":7118,"_70":69},"eZM2yF9i",{},[7114],{"_35":166,"_167":7115,"_169":7116,"_41":7117,"_70":69},[137],[2828],{},"Nürnberg, P. J. HOSS: An Environment to Support Structural Computing. PhD thesis, Department of Computer Science, Texas A&M University, College Station, TX, 1997.",{"_31":7120,"_33":7121},[],{"_35":160,"_37":7122,"_39":6598,"_41":7123,"_66":7124,"_68":7136,"_70":69},"dH6jW6ma",{},[7125,7130],{"_35":166,"_167":7126,"_169":7127,"_41":7129,"_70":69},[137],[7128],83,{},{"_35":919,"_167":7131,"_169":7133,"_41":7135,"_70":69},[7132],162,[7134],201,{},"Nürnberg, P. J., Grønbæk, K., Bucka-Lassen, D., Pedersen, C. A., and Reinert, O. A. A component-based open hypermedia approach to integrating structure services. New Review of Hypermedia and Multimedia (1999). Accepted for publication.",{"_31":7138,"_33":7139},[],{"_35":160,"_37":7140,"_39":6598,"_41":7141,"_66":7142,"_68":7152,"_70":69},"M4fmKLV3",{},[7143,7147],{"_35":166,"_167":7144,"_169":7145,"_41":7146,"_70":69},[137],[2261],{},{"_35":919,"_167":7148,"_169":7149,"_41":7151,"_70":69},[185],[7150],153,{},"Nürnberg, P. J., and Leggett, J. J. A vision for open hypermedia systems. Journal of Digital Information (JoDI). Special Issue on Open Hypermedia Systems 1, 2 (1997).",{"_31":7154,"_33":7155},[],{"_35":160,"_37":7156,"_39":6598,"_41":7157,"_66":7158,"_68":7169,"_70":69},"maeJ5TG2",{},[7159,7164],{"_35":166,"_167":7160,"_169":7161,"_41":7163,"_70":69},[137],[7162],53,{},{"_35":919,"_167":7165,"_169":7166,"_41":7168,"_70":69},[6950],[7167],169,{},"Nürnberg, P. J., Leggett, J. J., and Schneider, E. R. As we should have thought. In Proceedings of the ’97 ACM Conference on Hypertext, April 6-11, 1997, Southampton, UK (1997), pp. 96–101.",{"_31":7171,"_33":7172},[],{"_35":160,"_37":7173,"_39":6598,"_41":7174,"_66":7175,"_68":7184,"_70":69},"kRzSQ5ij",{},[7176,7180],{"_35":166,"_167":7177,"_169":7178,"_41":7179,"_70":69},[137],[7162],{},{"_35":919,"_167":7181,"_169":7182,"_41":7183,"_70":69},[6278],[6675],{},"Nürnberg, P. J., Schneider, E. R., and Leggett, J. J. Designing digital libraries for the hyper-literate age. Journal of Universal Computer Science 2, 9 (1996).",{"_31":7186,"_33":7187},[],{"_35":160,"_37":7188,"_39":6598,"_41":7189,"_66":7190,"_68":7200,"_70":69},"nogR1f1B",{},[7191,7195],{"_35":166,"_167":7192,"_169":7193,"_41":7194,"_70":69},[137],[240],{},{"_35":919,"_167":7196,"_169":7197,"_41":7199,"_70":69},[1412],[7198],132,{},"Park, S. Structural Properties of Hypertext. In Proceedings of the ’98 ACM Conference on Hypertext, June 20-24, 1998, Pittsburgh, PA (1998), pp. 180–187.",{"_31":7202,"_33":7203},[],{"_35":160,"_37":7204,"_39":6598,"_41":7205,"_66":7206,"_68":7217,"_70":69},"lWrW--pT",{},[7207,7211],{"_35":166,"_167":7208,"_169":7209,"_41":7210,"_70":69},[137],[3339],{},{"_35":919,"_167":7212,"_169":7214,"_41":7216,"_70":69},[7213],210,[7215],249,{},"Reich, S., Wiil, U. K., Nürnberg, P. J., Davis, H. C., Grønbæk, K., Anderson, K. M., Millard, D. E., and Haake, J. M. Addressing interoperability in open hypermedia: The design of the open hypermedia protocol. New Review of Hypermedia and Multimedia (1999). Accepted for publication.",{"_31":7219,"_33":7220},[],{"_35":160,"_37":7221,"_39":6598,"_41":7222,"_66":7223,"_68":7234,"_70":69},"d4YfUqaU",{},[7224,7228],{"_35":166,"_167":7225,"_169":7226,"_41":7227,"_70":69},[137],[7028],{},{"_35":919,"_167":7229,"_169":7231,"_41":7233,"_70":69},[7230],172,[7232],264,{},"Reinert, O., Bucka-Lassen, D., Pedersen, C. A., and Nürnberg, P. J. CAOS: A collaborative and open spatial structure service component with incremental spatial parsing. In Proceedings of the ’99 ACM Conference on Hypertext, February 21-25, 1999, Darmstadt, Germany (Feb. 1999), pp. 49–50.",{"_31":7236,"_33":7237},[],{"_35":160,"_37":7238,"_39":6598,"_41":7239,"_66":7240,"_68":7250,"_70":69},"A0f8tK2m",{},[7241,7245],{"_35":166,"_167":7242,"_169":7243,"_41":7244,"_70":69},[137],[3407],{},{"_35":919,"_167":7246,"_169":7247,"_41":7249,"_70":69},[6479],[7248],128,{},"Stotts, P. D., and Furuta, R. Hypertext 2000: Databases or documents? Electronic Publishing—Origination Dissemination and Design 4 (June 1991), 119–122.",{"_31":7252,"_33":7253},[],{"_35":160,"_37":7254,"_39":6598,"_41":7255,"_66":7256,"_68":7266,"_70":69},"O-YMGikl",{},[7257,7262],{"_35":166,"_167":7258,"_169":7259,"_41":7261,"_70":69},[137],[7260],44,{},{"_35":919,"_167":7263,"_169":7264,"_41":7265,"_70":69},[6533],[3376],{},"Thüring, M., Hannemann, J., and Haake, J. M. Hypermedia and cognition: Designing for comprehension. Communications of the ACM 38, 8 (Aug. 1995), 57–66.",{"_31":7268,"_33":7269},[],{"_35":160,"_37":7270,"_39":6598,"_41":7271,"_66":7272,"_68":7281,"_70":69},"_ws_sbH6",{},[7273,7277],{"_35":166,"_167":7274,"_169":7275,"_41":7276,"_70":69},[137],[1542],{},{"_35":919,"_167":7278,"_169":7279,"_41":7280,"_70":69},[7028],[6094],{},"Tompa, F. W. A Data Model for Flexible Hypertext Database Systems. ACM Transactions of Information Systems 7, 1 (Jan. 1989), 85–100.",{"_31":7283,"_33":7284},[],{"_35":160,"_37":7285,"_39":6598,"_41":7286,"_66":7287,"_68":7299,"_70":69},"d_4SMxnE",{},[7288,7292],{"_35":166,"_167":7289,"_169":7290,"_41":7291,"_70":69},[137],[1476],{},{"_35":919,"_167":7293,"_169":7295,"_41":7298,"_70":69},[185,7294],192,[7296,7297],191,301,{},"Trigg, R. A straw model for link traversal in open hypermedia systems. In Proceedings of the 4th Workshop on Open Hypermedia Systems, ACM Hypertext ’98 Conference, Pittsburgh, PA, June 20-24. Available as Report No. CS-98-01 from the Dept. of Computer Science, 6700 Aalborg University Esbjerg, Denmark (1998), pp. 69–62.",{"_31":7301,"_33":7302},[],{"_35":160,"_37":7303,"_39":6598,"_41":7304,"_66":7305,"_68":7315,"_70":69},"H0ZfrZpN",{},[7306,7311],{"_35":166,"_167":7307,"_169":7308,"_41":7310,"_70":69},[137],[7309],20,{},{"_35":919,"_167":7312,"_169":7313,"_41":7314,"_70":69},[6377],[2070],{},"Van Dyke Parunak, H. Don’t link me in: Set-based hypermedia for taxonomic reasoning. In Proceedings of the ’91 ACM Conference on Hypertext, Dec. 15-18, 1991, San Antonio, TX (1991), pp. 233–242.",{"_31":7317,"_33":7318},[],{"_35":160,"_37":7319,"_39":6598,"_41":7320,"_66":7321,"_68":7332,"_70":69},"ErxMUyyd",{},[7322,7326],{"_35":166,"_167":7323,"_169":7324,"_41":7325,"_70":69},[137],[7309],{},{"_35":919,"_167":7327,"_169":7329,"_41":7331,"_70":69},[7328],102,[7330],183,{},"Van Dyke Parunak, H. Hypercubes grow on trees (and other observations from the land of hypersets). In Proceedings of the ’93 ACM Conference on Hypertext, Nov. 14-18, 1993, Seattle, WA (1993), pp. 73–81.",{"_31":7334,"_33":7335},[],{"_35":160,"_37":7336,"_39":6598,"_41":7337,"_66":7338,"_68":7347,"_70":69},"UVwCubLJ",{},[7339,7343],{"_35":166,"_167":7340,"_169":7341,"_41":7342,"_70":69},[137],[987],{},{"_35":919,"_167":7344,"_169":7345,"_41":7346,"_70":69},[5591],[7296],{},"Wiil, U. K., and Nürnberg, P. J. Evolving hypermedia middleware services: Lessons and observations. In Proceedings of of the 1999 ACM Symposium on Applied Computing (SAC ’99), San Antonio, TX (Feb. 1999), pp. 427–436.",{"_31":7349,"_33":7350},[],{"_35":160,"_37":7351,"_39":6598,"_41":7352,"_66":7353,"_68":7362,"_70":69},"Ke-E0qei",{},[7354,7358],{"_35":166,"_167":7355,"_169":7356,"_41":7357,"_70":69},[137],[1573],{},{"_35":919,"_167":7359,"_169":7360,"_41":7361,"_70":69},[1013],[6258],{},"Wiil, U. K., and Østerbye, K., Eds. Proceedings of the ECHT ’94 Workshop on Open Hypermedia Systems (1994). Technical Report R-94-2038, Dept. of Computer Science, Aalborg University.",{"_35":870,"_37":7364,"_39":6598,"_41":7365,"_66":7366,"_68":7367,"_70":69},"v9cy-d2J",{"_273":2113},[],"REFERENCES",[279],"/records/fohm-a-fundamental-open-hypertext-model-for-investigating-interoperability-between-hypertext-domains","2025-07-06T21:35:17.922Z",{"_82":570},{},{"_37":544,"_95":53,"_54":7374,"_71":547,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,546],1772031973398,[149,544,547],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/fohm-a-fundamental-open-hypertext-model-for-investigating-interoperability-between-hypertext-domains\",\"bafy2bzaceazfbkeiizkojnccrl2op4rrtmd34c2k2g3ig6vwstm7aky6k7cnm\"]",{"_110":7379,"_147":7500,"_150":7501},{"_112":7380,"_131":132,"_133":7499,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":7381,"_37":7497},{"_28":7382,"_71":576,"_72":53,"_73":7493,"_54":7494,"_76":583,"_78":583,"_80":7495,"_84":7496,"_86":576,"_88":89},[7383,7390,7397,7404,7411,7418,7430,7437,7444,7451,7458,7465,7472,7479,7486],{"_31":7384,"_33":7385},[],{"_35":1875,"_37":7386,"_39":576,"_41":7387,"_66":7388,"_68":69,"_70":7389},"p4AMUIgQ",{"_273":323},[],"ipfs://bafkreiewyltfarlgdabtxg2xweqwqrjpgdfpqrnx2xtb5dy6674jrjuefm",{"_31":7391,"_33":7392},[],{"_35":160,"_37":7393,"_39":576,"_41":7394,"_66":7395,"_68":7396,"_70":69},"-DF73eNe",{},[],"Douglas C. Engelbart Stanford Research Institute Menlo Park, California",{"_31":7398,"_33":7399},[],{"_35":160,"_37":7400,"_39":576,"_41":7401,"_66":7402,"_68":7403,"_70":69},"XXw4jC7M",{},[],"May 24, 1962",{"_31":7405,"_33":7406},[],{"_35":160,"_37":7407,"_39":576,"_41":7408,"_66":7409,"_68":7410,"_70":69},"wf6V5Qjp",{},[],"Dr. Vannevar Bush Professor Emeritus Massachusetts Institute of Technology Cambridge, Massachusetts",{"_31":7412,"_33":7413},[],{"_35":160,"_37":7414,"_39":576,"_41":7415,"_66":7416,"_68":7417,"_70":69},"ecXgnTvS",{},[],"Dear Dr. Bush:",{"_31":7419,"_33":7420},[],{"_35":160,"_37":7421,"_39":576,"_41":7422,"_66":7423,"_68":7429,"_70":69},"SNRapKYU",{},[7424],{"_35":204,"_167":7425,"_169":7426,"_41":7427,"_70":7428},[6533],[208],{},"https://web.archive.org/web/20110730055322/http://sloan.stanford.edu/mousesite/Secondary/Bushframe.html","I wish permission from you to extract lengthy and definitely acknowledged quotes from your article, \"As We May Think,\" that appeared in The Atlantic Monthly, July, 1945. These quotes would appear in a report that I am writing for the Air Force Office of Scientific Research, and I am sending a parallel request to The Atlantic Monthly.",{"_31":7431,"_33":7432},[],{"_35":160,"_37":7433,"_39":576,"_41":7434,"_66":7435,"_68":7436,"_70":69},"Ff-7FExs",{},[],"For your information I am enclosing a relatively brief and quite general writeup describing the program that I am trying to develop here at Stanford Research Institute. The report which I am writing (and for which I am requesting quotation permission from you) is a detailed description of the conceptual structure that I have developed over the years to orient my pursuit of this objective of increasing the individual human's intellectual effectiveness. It will also contain a number of examples of the way in which new equipment can lead to new methods and improved effectiveness, to illustrate my more general (but nonnumerical) framework, and your article is quite the best that I have found in print to offer examples of this.",{"_31":7438,"_33":7439},[],{"_35":160,"_37":7440,"_39":576,"_41":7441,"_66":7442,"_68":7443,"_70":69},"6Ok4zA2B",{},[],"I might add that this article of yours has probably influenced me quite basically. I remember finding it and avidly reading it in a Red Cross library on the edge of the jungle on Leyte, one of the Phillipine [sic] Islands, in the Fall of 1945. Subsequently, l went back and finished my B.S. in E.E. after the war (Oregon State), and worked for the NACA at Moffett Field (near here) until 1951, when I got fed up with my goalless role. I formulated then the goal for which this program represents the pursuit vehicle, spent years in graduate school at the University of California (Berkeley), taught there a while, and finally ended up here-- choosing SRI as a place where I would have a good chance to work toward developing such a program. I had had almost nothing but negative reactions from people up to then, and for several years here, too.",{"_31":7445,"_33":7446},[],{"_35":160,"_37":7447,"_39":576,"_41":7448,"_66":7449,"_68":7450,"_70":69},"uLK39BOg",{},[],"But the climate has changed of late, and for two years I have personally been able to spend almost full time trying to lay the conceptual groundwork for launching a serious research program on \"human intellectual effectiveness.\" I think I have a good approach developed for such a program, and we are trying to get it supported and started. Our OSR support has been for half of my time in this pre-program study, and the report for them will hopefully lay out considerations and reasoning that can show most readers where the promise and possibilities are for future improvement of our intellectual capability, and what is a reasonable approach to pursue these possibilities.",{"_31":7452,"_33":7453},[],{"_35":160,"_37":7454,"_39":576,"_41":7455,"_66":7456,"_68":7457,"_70":69},"qMpJYwX8",{},[],"I re-discovered your article about three years ago, and was rather startled to realize how much I had aligned my sights along the vector you had described. I wouldn't be surprised at all if the reading of this article sixteen and a half years ago hadn't had a real influence upon the course of my thoughts and actions.",{"_31":7459,"_33":7460},[],{"_35":160,"_37":7461,"_39":576,"_41":7462,"_66":7463,"_68":7464,"_70":69},"7jOFHNXI",{},[],"If you still have interest in this area and have the time and energy to give it some occasional consideration, l would be most happy to send you a copy of the report. (It is more than just a report to a government agency. For me it is more the public debut of a dream, and the overdue birth attests to my emotional involvement.)",{"_31":7466,"_33":7467},[],{"_35":160,"_37":7468,"_39":576,"_41":7469,"_66":7470,"_68":7471,"_70":69},"IBdD-V09",{},[],"Thank you for your consideration.",{"_31":7473,"_33":7474},[],{"_35":160,"_37":7475,"_39":576,"_41":7476,"_66":7477,"_68":7478,"_70":69},"vp1UxcBQ",{},[],"Sincerely,",{"_31":7480,"_33":7481},[],{"_35":160,"_37":7482,"_39":576,"_41":7483,"_66":7484,"_68":7485,"_70":69},"UtuD5XVo",{},[],"Douglas C. Engelbart",{"_31":7487,"_33":7488},[],{"_35":160,"_37":7489,"_39":576,"_41":7490,"_66":7491,"_68":7492,"_70":69},"XcfL-Vuc",{},[],"Senior Research Engineer",[53],"/records/letter-to-vannevar-bush-from-engelbart",{"_82":592},{},{"_37":573,"_95":53,"_54":7498,"_71":576,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,575],1772031973221,[149,573,576],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/letter-to-vannevar-bush-from-engelbart\",\"bafy2bzaceapz6vfyjvnouujsswjhsgtdhxldaa6er7ertvvtf2uc5anyy7rjm\"]",{"_110":7503,"_147":8494,"_150":8495},{"_112":7504,"_131":132,"_133":8493,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":7505,"_37":8491},{"_28":7506,"_71":598,"_72":53,"_73":8487,"_54":8488,"_76":604,"_78":604,"_80":8489,"_84":8490,"_86":598,"_88":89},[7507,7514,7521,7528,7535,7542,7549,7556,7563,7570,7577,7584,7591,7598,7605,7612,7619,7626,7633,7640,7647,7654,7661,7668,7675,7682,7689,7696,7703,7710,7717,7724,7731,7738,7745,7752,7759,7766,7773,7780,7787,7857,7952,7987,8099,8169,8239,8309,8448],{"_31":7508,"_33":7509},[],{"_35":160,"_37":7510,"_39":598,"_41":7511,"_66":7512,"_68":7513,"_70":69},"XYF1sRch",{},[],"[Source: AUG. 24/11:00-12:30/GOLD ROOM 84 • ACM 20th National Conference/1965 SESSION 4: Complex Information Processing T. H. Nelson Vassar College, Poughkeepsie, N.Y. ]",{"_31":7515,"_33":7516},[],{"_35":160,"_37":7517,"_39":598,"_41":7518,"_66":7519,"_68":7520,"_70":69},"LSUAdnex",{},[],"THE KINDS OF FILE structures required if we are to use the computer for personal files and as an adjunct to creativity are wholly different in character from those customary in business and scientific data processing. They need to provide the capacity for intricate and idiosyncratic arrangements, total modifiability, undecided alternatives, and thorough internal documentation.",{"_31":7522,"_33":7523},[],{"_35":160,"_37":7524,"_39":598,"_41":7525,"_66":7526,"_68":7527,"_70":69},"PUc18Zjn",{},[],"The original idea was to make a file for writers and scientists, much like the personal side of Bush's Memex, that would do the things such people need with the richness they would want. But there are so many possible specific functions that the mind reels. These uses and considerations become so complex that the only answer is a simple and generalized building-block structure, user-oriented and wholly general-purpose.",{"_31":7529,"_33":7530},[],{"_35":160,"_37":7531,"_39":598,"_41":7532,"_66":7533,"_68":7534,"_70":69},"rKcvID-D",{},[],"The resulting file structure is explained and examples of its use are given. It bears generic similarities to list-processing systems but is slower and bigger. It employs zippered lists plus certain facilities for modification and spin-off of variations. This is technically accomplished by index manipulation and text patching, but to the user it acts like a multifarious, polymorphic, many-dimensional, infinite blackboard.",{"_31":7536,"_33":7537},[],{"_35":160,"_37":7538,"_39":598,"_41":7539,"_66":7540,"_68":7541,"_70":69},"tbcRmSb4",{},[],"The ramifications of this approach extend well beyond its original concerns, into such places as information retrieval and library science, motion pictures and the programming craft; for it is almost everywhere necessary to deal with deep structural changes in the arrangements of ideas and things.",{"_31":7543,"_33":7544},[],{"_35":160,"_37":7545,"_39":598,"_41":7546,"_66":7547,"_68":7548,"_70":69},"Z1Qivyss",{},[],"I want to explain how some ideas developed and what they are. The original problem was to specify a computer system for personal information retrieval and documentation, able to do some rather complicated things in clear and simple ways. The investigation gathered generality, however, and has eventuated in a number of ideas. These are an information structure, a file structure, and a file language, each progressively more complicated. The information structure I call zippered lists; the file structure is the ELF, or ]Evolutionary Lis't File; and the file language (proposed) is called PRIDE.",{"_31":7550,"_33":7551},[],{"_35":160,"_37":7552,"_39":598,"_41":7553,"_66":7554,"_68":7555,"_70":69},"mpmbIbW4",{},[],"In this paper I will explain the original problem. Then I will explain why the problem is not simple, and why the solution (a file structure) must yet be very simple. The file structure suggested here is the Evolutionary List File, to be built of zippered lists. A number of uses will be suggested for such a file, to show the breadth of its potential usefulness. Finally, I want to explain the philosophical implications of this approach for information retrieval and data structure in a changing world.",{"_31":7557,"_33":7558},[],{"_35":160,"_37":7559,"_39":598,"_41":7560,"_66":7561,"_68":7562,"_70":69},"Lb7OHzRA",{},[],"This work was begun in 1960 - without any assistance. Its purpose was to create techniques for handling personal file systems and manuscripts in progress. These two purposes are closely related and not sharply distinct. Many writers and research professionals have files or collections of notes which are tied to manuscripts in progress. Indeed, often personal files shade into manuscripts, and the assembly of textual notes becomes the writing of text without a sharp break.",{"_31":7564,"_33":7565},[],{"_35":160,"_37":7566,"_39":598,"_41":7567,"_66":7568,"_68":7569,"_70":69},"LFdaUqkz",{},[],"I knew from my own experiment what can be done for these purposes with card file, notebook, index tabs, edge-punching, file folders, scissors and paste, graphic boards, index-strip frames, Xerox machine and the roll-top desk. My intent was not merely to computerize these tasks but to think out (and eventually program) the dream file: the file system that would have every feature a novelist or absent-minded professor could want, holding everything he wanted in just the complicated way he wanted it held, and handling notes and manuscripts in as subtle and complex ways as he wanted them handled.",{"_31":7571,"_33":7572},[],{"_35":160,"_37":7573,"_39":598,"_41":7574,"_66":7575,"_68":7576,"_70":69},"ZL16mUB_",{},[],"Only a few obstacles impede our using computer-based systems for these purposes. These have been high cost, little sense of need, and uncertainty about system design.",{"_31":7578,"_33":7579},[],{"_35":160,"_37":7580,"_39":598,"_41":7581,"_66":7582,"_68":7583,"_70":69},"x4_yva5-",{},[],"The costs are now down considerably. A small computer with mass memory and video-type display now costs $37,000; amortized over time this would cost less than a secretary, and several people could use it around the clock. A larger installation servicing an editorial office or a newspaper morgue, or a dozen scientists or scholars, could cost proportionately less and give more time to each user.",{"_31":7585,"_33":7586},[],{"_35":160,"_37":7587,"_39":598,"_41":7588,"_66":7589,"_68":7590,"_70":69},"tbiZYrGw",{},[],"The second obstacle, sense of need, Is a matter of fashion. Despite changing economies, it is fashionably believed that computers are possessed only by huge organizations to be used only for vast corporate tasks or intricate scientific calculations. As long as people think that, machines will be brutes and not friends, bureaucrats and not helpmates. But since (as I will indicate) computers could do the dirty work of personal file and text handling, and do it with richness and subtlety beyond anything we know, there ought to be a sense of need. Unfortunately, there are no ascertainable statistics on the amount of time we waste fussing among papers and mislaying things. Surely half the time spent in writing is spent physically rearranging words and paper and trying to find things already written; if 95% of this time could be saved, it would only take half as long to write something.",{"_31":7592,"_33":7593},[],{"_35":160,"_37":7594,"_39":598,"_41":7595,"_66":7596,"_68":7597,"_70":69},"3Ec67mSH",{},[],"The third obstacle, design, is the only substantive one, the one to which this paper speaks.",{"_31":7599,"_33":7600},[],{"_35":160,"_37":7601,"_39":598,"_41":7602,"_66":7603,"_68":7604,"_70":69},"GLlaNPbS",{},[],"Let me speak first of the automatic personal filing system. This idea is by no means new. To go back only as far as 1945, Vannevar Bush, in his famous article \"As We May Think \"1 , described a system of this type. Bush's paper is better remembered for its predictions in the field of information retrieval, as he foresaw the spread and power of automatic document handling and the many new indexing techniques it would necessitate. But note his predictions for personal filing:",{"_31":7606,"_33":7607},[],{"_35":160,"_37":7608,"_39":598,"_41":7609,"_66":7610,"_68":7611,"_70":69},"34I-c2bl",{},[],"\"Consider a future device for individual use, which is a sort of mechanized private file and library. It needs a name, and, to coin one at random, \"memex\" will do. A memex is a device in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility. It is an enlarged intimate~ supplement to his memory.",{"_31":7613,"_33":7614},[],{"_35":160,"_37":7615,"_39":598,"_41":7616,"_66":7617,"_68":7618,"_70":69},"qfIjtMrs",{},[],"\"It consists of a desk, and while it can pres~mebly be operated from a distance, it is primarily the piece of furniture at which he works. On the top are slanting translucent screens, on which material can be projected for convenient reading. There is a keyboard, and sets of buttons and levers. Otherwise it looks like an ordinary desk.",{"_31":7620,"_33":7621},[],{"_35":160,"_37":7622,"_39":598,"_41":7623,"_66":7624,"_68":7625,"_70":69},"iaQSpfap",{},[],"\"A special button transfers him immediately to the first page of the index. Any given book of his library / and presumably other textual material, such as notes/ can thus be called up and consulted with far greater facility than if it were taken from a shelf. As he has several projection positions, he can leave one item in position while he calls up another. He can add marginal notes and comments, .... \" (i, 106-7)",{"_31":7627,"_33":7628},[],{"_35":160,"_37":7629,"_39":598,"_41":7630,"_66":7631,"_68":7632,"_70":69},"WR3BJhXd",{},[],"Understanding that such a machine required new kinds of filing arrangements, Bush stressed his file's ability to store related materials in associative trails, lists or chains of documents joined together.",{"_31":7634,"_33":7635},[],{"_35":160,"_37":7636,"_39":598,"_41":7637,"_66":7638,"_68":7639,"_70":69},"aqdQeHU1",{},[],"\"When the user is building a trail, he names it, inserts the name in his code book, and taps it out on his keyboard. Before him are the two items to be joined, projected onto adjacent viewing positions. At the bottom of each there are a number of blank code spaces, and a pointer is set to indicate one of these on each item. The user taps a single key, and the items are permanently joined ....",{"_31":7641,"_33":7642},[],{"_35":160,"_37":7643,"_39":598,"_41":7644,"_66":7645,"_68":7646,"_70":69},"nLbezgSK",{},[],"\"Thereafter, at any time, when one of these items is in view, the other can be instantly recalled merely by tapping a button below the corresponding code space. Moreover, when numerous items have been thus joined together to form a trail, they can be reviewed in turn, rapidly or slowly, by deflecting a lever like that used for turning the pages of a book. It is exactly as though the physical items had been gathered together from widely separated sources and bound together to form a new book. It is more than this, for any item can be joined into numerous trails ....",{"_31":7648,"_33":7649},[],{"_35":160,"_37":7650,"_39":598,"_41":7651,"_66":7652,"_68":7653,"_70":69},"grmPYWGl",{},[],"\"Thus he goes, building a trail of many items. Occasionally he inserts a comment of his own, either linking it into the main trail or joining it by a side trail to a particular item .... \" (1, 107)",{"_31":7655,"_33":7656},[],{"_35":160,"_37":7657,"_39":598,"_41":7658,"_66":7659,"_68":7660,"_70":69},"_edI3oUg",{},[],"Two decades later, this machine is still unavailable*.",{"_31":7662,"_33":7663},[],{"_35":160,"_37":7664,"_39":598,"_41":7665,"_66":7666,"_68":7667,"_70":69},"NNOWzSFE",{},[],"The hardware is ready. Standard computers can handle huge bodies of written information, storing them on magnetic recording media and displaying their contents on CRT consoles, which far outshine desktop projectors. But no programs, no file software are standing ready to do the intricate filing job (keeping track of associative trails and other stKuctures) Ithat the active scientist or thinker wants and needs. While WallaceZ reports that the System Development Corporation has found it worthwhile to give its employees certain limited computer facilities for their own filing systems, this is a bare beginning.",{"_31":7669,"_33":7670},[],{"_35":160,"_37":7671,"_39":598,"_41":7672,"_66":7673,"_68":7674,"_70":69},"s_rj_pYb",{},[],"Let us consider the other desideratum, manuscript handling. The remarks that follow are intended to apply to all forms of writing, including fiction, philosophy, sermons, news and technical writing.",{"_31":7676,"_33":7677},[],{"_35":160,"_37":7678,"_39":598,"_41":7679,"_66":7680,"_68":7681,"_70":69},"rxIEh9Rs",{},[],"The problems of writing are little understood, even by writers. Systems analysis in this area is scanty; as elsewhere, the best doers may not understand what they do. Although there is considerable anecdote and lore about the different physical manuscript and file techniques of different authors, literary tradition demerits any concern with technical systems as detracting from \"creativity.\" (Conversely, technical people do not always appreciate the difficulty of organizing text, since in technical writing much of the organization and phraseology is given, or appears to be.) But in the computer sciences we are profoundly aware of the importance of systems details, and of the variety of consequences for both quality and quantity of work that result from different systems. Yet to design and evaluate systems for writing, we need to know what the process of writing is.",{"_31":7683,"_33":7684},[],{"_35":160,"_37":7685,"_39":598,"_41":7686,"_66":7687,"_68":7688,"_70":69},"Ik6nj42Y",{},[],"There are three false or inadequate theories of how writing is properly done. The first is that writing is a matter of inspiration. While inspiration is useful, it is rarely enough in itself. \"Writing is 10% inspiration, 90% perspiration,\" is a common saying. But this leads us to the second false theory, that \"writing consists of applying the seat of the pants to the seat of the chair.\" Insofar as sitting facilitates work, this view seems reasonable, but it also suggests that what is done while sitting is a matter of comparative indifference; probably not.",{"_31":7690,"_33":7691},[],{"_35":160,"_37":7692,"_39":598,"_41":7693,"_66":7694,"_68":7695,"_70":69},"VYSxYixk",{},[],"The third false theory is that all you really need is a good outline, created on prior consideration, and that if the outline is correctly followed the required text will be produced. For most good writers this theory is quite wrong. Rarely does the original outline predict well what headings and sequence will create the effects desired: the balance of emphasis, sequence of interrelating points, texture of insight, rhythm, etc. We may better call the outlining process inductive: certain interrelations appear to the author in the material itself, some at the outset and some as he works. He can only decide which to emphasize, which to use as unifying ideas and principles, and which to slight or delete, by trying. Outlines in general are spurious, made up after the fact by examining the segmentation of a finished work. If a finished work clearly follows an outline, that online probably has been han~nered out of many inspirations, comparisons and tests .",{"_31":7697,"_33":7698},[],{"_35":160,"_37":7699,"_39":598,"_41":7700,"_66":7701,"_68":7702,"_70":69},"1OWtMclV",{},[],"Between the inspirations, then, and during the sitting, the task of writing is one of rearrangement and reprocessing, and the real outline develops slowly. The original ~rude or fragmentary texts created at the outset generally undergo many revision processes before they are finished. Intellectually they are pondere~ juxtaposed, compared, adapted, transposed, and judged; mechanically they are copied, overwritten with revision markings, rearranged and copied again. This cycle may be repeated many times. The whole grows by trial and error in the processes of arrangement, comparison and retrenchment. By examining and mentally noting many different versions, some whole but most fragmentary the intertwining and organizing of the final written work gradually takes place***.",{"_31":7704,"_33":7705},[],{"_35":160,"_37":7706,"_39":598,"_41":7707,"_66":7708,"_68":7709,"_70":69},"Qi8odcDV",{},[],"Certain things have been done in the area of computer manuscript handling. IBM recently announced its \"Administrative Terminal System\"5,6,7, 8 which permits the storage of unfinished sections of text in computer memory, permits various modifications by the user, and types up the final draft with page numbers, right justification and headers.",{"_31":7711,"_33":7712},[],{"_35":160,"_37":7713,"_39":598,"_41":7714,"_66":7715,"_68":7716,"_70":69},"uLpDxBlL",{},[],"While this is a good thing, its function for manuscripts is cosmetic rather than organizing. Such a system can be used only with textual sections which are already well organized, the visible part of the iceberg. The major and strenuous part of such writing must already have been done.",{"_31":7718,"_33":7719},[],{"_35":160,"_37":7720,"_39":598,"_41":7721,"_66":7722,"_68":7723,"_70":69},"1BMXyKIC",{},[],"If a writer is really to be helped by an automated system, it ought to do more than retype and transpose: it should stand by him during the early periods of muddled confusion, when his ideas are scraps, fragments, phrases, and contradictory overall designs. And it must help him through to the final draft with every feasible mechanical aid-- making the fragments easy to find, and making easier the tentative sequencing and juxtaposing and comparing.",{"_31":7725,"_33":7726},[],{"_35":160,"_37":7727,"_39":598,"_41":7728,"_66":7729,"_68":7730,"_70":69},"XvRhpM44",{},[],"It was for these two purposes, taken together-- personal filing and manuscript assembly-- that the following specifications were drawn up.",{"_31":7732,"_33":7733},[],{"_35":160,"_37":7734,"_39":598,"_41":7735,"_66":7736,"_68":7737,"_70":69},"9eRQ7C_g",{},[],"Here were the preliminary specifications of the system: It would provide an up-to-date index of its own contents (supplanting the \"code book\" suggested by Bush). It would accept large and growing bodies of text and commentary, listed in such complex forms as the user might stipulate. No hierarchical file relations were to be built in; the system would hold any shape imposed on it. It would file texts in any form and arrangement desired-- combining, at will, the functions of the card file, loose-leaf notebook, and so on. It would file under an unlimited number of categories. It would provide for filing in Bush trails. Besides the file entries themselves, it would hold co~mnentaries and explanations connected with them. These annotations would help the writer or scholar keep track of his previous ideas, reactions and plans, often confusingly forgotten.",{"_31":7739,"_33":7740},[],{"_35":160,"_37":7741,"_39":598,"_41":7742,"_66":7743,"_68":7744,"_70":69},"9myc6c-r",{},[],"In addition to these static facilities, the system would have various provisions for change. The user must be able to change both the contents of his file and the way they are arranged. Facilities would be available for the revising and rewording of text. Moreover, changes in the arrangements of the file's component parts should be possible, including changes in sequence, labelling, indexing and comments.",{"_31":7746,"_33":7747},[],{"_35":160,"_37":7748,"_39":598,"_41":7749,"_66":7750,"_68":7751,"_70":69},"tD5TybwB",{},[],"It was also intended that the system would allow index manipulations which we may call dynamic outlining (or dynamic ~indexing). Dynamic outlining uses the change in one text sequence to guide an automatic change in another text sequence. That is, changing an outline (or an index) changes the sequence of the main text which is linked with it. This would permit a writer to create new drafts with a relatively small amount of effort, not counting rewordings.",{"_31":7753,"_33":7754},[],{"_35":160,"_37":7755,"_39":598,"_41":7756,"_66":7757,"_68":7758,"_70":69},"zmcZdmQl",{},[],"However, because it is necessary to examine changes and new arrangements before deciding to use or keep them, the system must not commit the user to a new version until he is ready. Indeed, the system would have to provide spin-off facilities, allowing a draft of a work to be preserved while its successor was created. Consequently the system must be able to hold several-- in fact, many-- different versions of the same sets of materials. Moreover, these alternate versions would remain indexed to one another, so that however he might have changed their sequences, the user could compare their equivalent parts.",{"_31":7760,"_33":7761},[],{"_35":160,"_37":7762,"_39":598,"_41":7763,"_66":7764,"_68":7765,"_70":69},"6oQck4er",{},[],"Three particular features, then, would be specially adapted to useful change. The system would be able to sustain changers in the bulk and block arrangements of its contents. It would permit dynamic outlining. And it would permit the spinoff of many different drafts, either successors or variants, all to remainwithin the file for comparison or use as long as needed. These features we may call evolutionary.",{"_31":7767,"_33":7768},[],{"_35":160,"_37":7769,"_39":598,"_41":7770,"_66":7771,"_68":7772,"_70":69},"83Wwrsk7",{},[],"The last specification, of course, one that emerged from all the others, was that it should not be complicated.",{"_31":7774,"_33":7775},[],{"_35":160,"_37":7776,"_39":598,"_41":7777,"_66":7778,"_68":7779,"_70":69},"OEn5EZSC",{},[],"These were the original desiderata. It was not expected at first that a system for this purpose would have wider scope of application; these jobs seemed to be quite enough. As work continued, however, the structure began to look more simple, powerful and general, and a variety of new possible uses appeared. It became apparent that the System might be suited to many unplanned applications involving multiple categories, text summaries or other parallel documents, complex data structures requiring human attention, and files whose relations would be in continuing change.",{"_31":7781,"_33":7782},[],{"_35":160,"_37":7783,"_39":598,"_41":7784,"_66":7785,"_68":7786,"_70":69},"g9s62Dw_",{},[],"Note that in the discussion that follows we will pretend we can simply see into the machine, and not worry for the present about how we can actually see, understand and manipulate these files. These are problems of housekeeping, I/0 and display, for which many solutions are possible.",{"_31":7788,"_33":7852},[7789,7796,7803,7810,7817,7824,7831,7838,7845],{"_31":7790,"_33":7791},[],{"_35":160,"_37":7792,"_39":598,"_41":7793,"_66":7794,"_68":7795,"_70":69},"50U-4Q6p",{},[],"What was required we may call an evolutionary file structure: a file structure that can be shaped into various forms, changed from one arrangement to another in accordance with the user's changing need. It was apparent also that some type of list structure was necessary. Making the file out of lists would allow different categories of personal notes, separate drafts, outlines and master indices all to be handled as lists of some sort; their segments could then be manipulated through automatic handling of index numbers. The resulting file structure I will, accordingly, call the Evolutionary List File, or ELF, since it is an evolutionary file structure constructed with lists. The system proposed here is not the only ELF possible. It is built upon a specific technique of attaching lists together which has a natural resistance to becoming confused and messy.",{"_31":7797,"_33":7798},[],{"_35":160,"_37":7799,"_39":598,"_41":7800,"_66":7801,"_68":7802,"_70":69},"Ys5cFmxC",{},[],"As computer-based systems grow in capability and diversity of uses, they tend to become more and more cluttered with niggling complications, hidden passageways, and lurking, detailed interlocks, restrictions, specializations, provisos. These should be forsworn, if possible, in the system under discussion, so that it might be attractive to laymen (including artists and writers) who feel unkindly disposed toward computers. It should readily adapt to their own styles of handling things, imposing few conventions or methods of use. How could this imposition be avoided? And among so many interesting and possible system functions and file relations, how may the users know what connections to make, how may they understand what they are doing, and how may they avoid muddling and losing the things they are working with?",{"_31":7804,"_33":7805},[],{"_35":160,"_37":7806,"_39":598,"_41":7807,"_66":7808,"_68":7809,"_70":69},"dkkglbl1",{},[],"The answer, I think you see, is to choose a very simple structure that can be used and compounded in many different ways. The basic arrangement chosen for these purposes is an information structure I will refer to as zippered lists. (We might call it permutation-invariant one-for-one inter-list entry-linking, but that is not necessary.)",{"_31":7811,"_33":7812},[],{"_35":160,"_37":7813,"_39":598,"_41":7814,"_66":7815,"_68":7816,"_70":69},"adyWF1ze",{},[],"There are only three kinds of things in the zippered-list ELF, with no predetermined relations among them-- no hierarchies, machine-based features or trick exceptions. The system is user-oriented and open-faced, and its clear and simple rules may be adapted to all purposes.",{"_31":7818,"_33":7819},[],{"_35":160,"_37":7820,"_39":598,"_41":7821,"_66":7822,"_68":7823,"_70":69},"Ts1nfhXQ",{},[],"The ELF has three elements: entries, lists and links. An entry is a discrete unit of information designated by the user. It can be a piece of text (long or short), a string of symbols, a picture or a control designation for physical objects or operations.",{"_31":7825,"_33":7826},[],{"_35":160,"_37":7827,"_39":598,"_41":7828,"_66":7829,"_68":7830,"_70":69},"49jb63ve",{},[],"A list is an ordered set of entries designated by the user. A given entry may be in any number of lists.",{"_31":7832,"_33":7833},[],{"_35":160,"_37":7834,"_39":598,"_41":7835,"_66":7836,"_68":7837,"_70":69},"j4TmbHCR",{},[],"A link is a connector, designated by the user, between two particular entries which are in different lists; Figure I. An entry in one list may be linked to only one entry in another list.",{"_31":7839,"_33":7840},[],{"_35":160,"_37":7841,"_39":598,"_41":7842,"_66":7843,"_68":7844,"_70":69},"bTy60-BH",{},[],"On the left we see two zippered lists. Between the entries of list A and those of B are dashed lines, representing the links between the two lists. On the right is the table of links as it might look to a machine. The machine can read this table from right to left or left to right, finding entries in B that correspond to given entries in A, or vice versa. A change in the sequence of either list, or additions to either list, will not: change the links that stand between them. Changes in the link structure will occur only if the user specifically changes the links, or if he destroys entries which are linked to others.",{"_31":7846,"_33":7847},[],{"_35":160,"_37":7848,"_39":598,"_41":7849,"_66":7850,"_68":7851,"_70":69},"Gm2FAclR",{},[],"To be technical, then, two lists are zippered if there are any pairwise links between their respective elements, each element is in no more than one link pair, and these links are unaffected by permutation of the lists, remaining affixed to the same pairs of elements. It is not required that the two lists be of the same length, or, even if they are, that all entries have a link to the other list.",{"_35":870,"_37":7853,"_39":598,"_41":7854,"_66":7855,"_68":7856,"_70":69},"wDZc2s7b",{},[],"Elements of the ELF",{"_31":7858,"_33":7947},[7859,7866,7881,7896,7911,7926,7933,7940],{"_31":7860,"_33":7861},[],{"_35":160,"_37":7862,"_39":598,"_41":7863,"_66":7864,"_68":7865,"_70":69},"jUnrNB7J",{},[],"Zippered lists are an information structure; the Evolutionary List File is a file structure. The ELF described in this paper holds its contents exclusively as zippered (or unzippered) lists. But the file structure must also include a set of operations by which it may be modified. These file operations exist for creating, adjusting or removing the entry, list and link, and for manipulating the sequence relation. An ELF is actually any machine which will, on command, carry out the basic operations on entry, list, link and sequence.",{"_31":7867,"_33":7868},[],{"_35":160,"_37":7869,"_39":598,"_41":7870,"_66":7871,"_68":7880,"_70":69},"Uo0aqLc1",{},[7872,7876],{"_35":166,"_167":7873,"_169":7874,"_41":7875,"_70":69},[137],[221],{},{"_35":919,"_167":7877,"_169":7878,"_41":7879,"_70":69},[137],[221],{},"Entries**.** The user may create new entries at any time, putting anything in them that he thinks appropriate. Entries ~y be combined or divided (unless indivisible, like objects, commands, etc.) Entries may be put in any list, and the same entry may be put in different lists. The user may direct that entries of one list be automatically copied onto another list, without affecting the original list.",{"_31":7882,"_33":7883},[],{"_35":160,"_37":7884,"_39":598,"_41":7885,"_66":7886,"_68":7895,"_70":69},"WYIKHmRk",{},[7887,7891],{"_35":166,"_167":7888,"_169":7889,"_41":7890,"_70":69},[137],[201],{},{"_35":919,"_167":7892,"_169":7893,"_41":7894,"_70":69},[137],[201],{},"Lists. The user may create lists and assign entries to them. He may at will make new copies of lists. He may rearrange the sequence of a list, or copy the list and change the sequence of that copy. Lists may be combined; lists may be cut into sublists.",{"_31":7897,"_33":7898},[],{"_35":160,"_37":7899,"_39":598,"_41":7900,"_66":7901,"_68":7910,"_70":69},"ja47TNVN",{},[7902,7906],{"_35":166,"_167":7903,"_169":7904,"_41":7905,"_70":69},[137],[201],{},{"_35":919,"_167":7907,"_169":7908,"_41":7909,"_70":69},[137],[201],{},"Links. Ths user may create links between entries that are in different lists. Any number of legal links may be created, although the upper limit of links between any two lists is determined by the l-for-I rule. When an entry or a list is copied into a list, links will remain between parent and daughter entries. Moreover, after a list-copying operation, the daughter list will have the same links to all other lists as does the parent list.",{"_31":7912,"_33":7913},[],{"_35":160,"_37":7914,"_39":598,"_41":7915,"_66":7916,"_68":7925,"_70":69},"QeUcKKO1",{},[7917,7921],{"_35":166,"_167":7918,"_169":7919,"_41":7920,"_70":69},[137],[1476],{},{"_35":919,"_167":7922,"_169":7923,"_41":7924,"_70":69},[137],[1476],{},"Sequences. The user may put a list in any sequence he wishes. (A copied list will maintain the original sequence until modified.) Sequences may be transferred between lists via the links: if the sequence of A is transferred to B, each entry of A linked to an entry in B takes tile sequential position of its linked entry in B.",{"_31":7927,"_33":7928},[],{"_35":160,"_37":7929,"_39":598,"_41":7930,"_66":7931,"_68":7932,"_70":69},"BZaEupmx",{},[],"No definite meaning is assigned to these entities or operations by the system; the user is free to let them mean anything he likes. A list may be a category, trail, index, dialogue, catalogue or poem, and lists may be assembled into larger structures. The ELF may be thought of as a place; not a machine, but a piece of stationery or office equipment with many little locations which may be rearranged with regard to one another****.",{"_31":7934,"_33":7935},[],{"_35":160,"_37":7936,"_39":598,"_41":7937,"_66":7938,"_68":7939,"_70":69},"NVuJx_Bu",{},[],"Note that zippered lists generate only one of various possible Evolutionary List Files. Indeed, the description of the file structure given here is in some ways restrictive: the ELF could take a number of other, closely similar forms and still be much the same thing. For example, it would be possible to allow subentries and superentries into the file, to behave and link up like normal entries, even though they contained or were contained in other entries. But the equivalent can be done with the current system. Another possibility would be to allow links other than 1-for-l; these could be modal, the different link-modes having different meanings to the user. Or we might make it an evolutionary network file, allowing any two entries to be connected. Or, besides such general changes in the rules, plausible changes and accessory functions for any purposes could be introduced outside the given file structure, even including modifications and widgets to do some of the same things \"more easily.\"",{"_31":7941,"_33":7942},[],{"_35":160,"_37":7943,"_39":598,"_41":7944,"_66":7945,"_68":7946,"_70":69},"DiP2Qcqn",{},[],"But to the user such complication might render the system far less handy or perspicuous. The ELF, with its associated techniques as described above, is simple and unified. Many tasks can be handled within the file structure. This means it can be of particular benefit to people who want to learn without complications and use it in ways they understand. For psychological, rather than technical reasons, the system should be lucid and simple. I believe that this ELF best meets these requirements.",{"_35":870,"_37":7948,"_39":598,"_41":7949,"_66":7950,"_68":7951,"_70":69},"twcRd193",{},[],"The ELF's File Operations",{"_31":7953,"_33":7982},[7954,7961,7968,7975],{"_31":7955,"_33":7956},[],{"_35":160,"_37":7957,"_39":598,"_41":7958,"_66":7959,"_68":7960,"_70":69},"xVp10V6x",{},[],"Since the ELF description above bears some resemblance to the list languages, such as IPL, SLIP, etc., a distinction should be drawn. These list languages ~ are particularly suited to processing data, fast and iteratively, whose elements are manipulable in Newell-Shaw-Simon lists. Essentially they my be thought of as organizations of memory which facilitate sequential operations on unpredictably branching or hierarchical data. These data may change far too quickly for human intervention. Evolutionary file structures, and the ELF in particular, are designed to be changed piecemeal by a human individual. While it might be convenient to program an ELF in one of these languages, the low speed at which user file commands need to be executed makes such high-powered implementation unnecessary; the main problem is to keep track of the file's arrangements, not to perform computation on its contents. Although work has been done to accomodate the list-language approach to larger chunks of material than usual I0, the things people will want to put into an ELF will typically be too big for core memory.",{"_31":7962,"_33":7963},[],{"_35":160,"_37":7964,"_39":598,"_41":7965,"_66":7966,"_68":7967,"_70":69},"XvLHpeZJ",{},[],"The ELF does in fact share some of the problems of the list languages: not available-storage accounting or garbage collection (concerns associated with organization of fast memory for processing, which may be avoided at slower speeds), but the problems of checkout for disposal (what other lists is an entry on?) and list naming. The former problem is rather straightforwardly solved II, P\" 164; the latter is complicated in ways we cannot cover here.",{"_31":7969,"_33":7970},[],{"_35":160,"_37":7971,"_39":598,"_41":7972,"_66":7973,"_68":7974,"_70":69},"XjfzIq33",{},[],"The ELF appears to be closest, topologically and in other organizing features, to the Multilist system described by Prywes and Gray 12. Like that system, it permits putting entries in many different lists at once. However, in current intent 13 that system is firmly hierarchical, and thus somewhat removed from the ELF's scope of application. Another closely related system is the Integrated Data Store of Bachmanl 4,15,16,17,18; this is intended as a hardware-software system for disc I/0 and storage arrangement, but in its details it seems the ELF's close relative. Each of these systems has a connection logic that might be feasible as a basis for an ELF different from this one. Or, either might prove a convenient programming base for the implementation of this file structure.",{"_31":7976,"_33":7977},[],{"_35":160,"_37":7978,"_39":598,"_41":7979,"_66":7980,"_68":7981,"_70":69},"hHtIze5D",{},[],"Another obvious technical question must be considered. How can the ELF allow \"unlimited\" copies of entries and lists? By patching techniques, of course. Variant entries and lists can take virtually no space, being modification data plus pointers to the original. When a modified version of a list or entry is created, the machine patches the original with the changes necessary to make the modified version: Figure 2.",{"_35":870,"_37":7983,"_39":598,"_41":7984,"_66":7985,"_68":7986,"_70":69},"9CEb7iet",{},[],"Technical Aspects",{"_31":7988,"_33":8094},[7989,7996,8003,8010,8017,8024,8031,8038,8045,8052,8059,8066,8073,8080,8087],{"_31":7990,"_33":7991},[],{"_35":160,"_37":7992,"_39":598,"_41":7993,"_66":7994,"_68":7995,"_70":69},"v8BHYmui",{},[],"In the discussion that follows, we will examine various possible applications of zippered lists and the ELF, and postpone discussing the file language they require. Finally we will return to this problem, and describe the file language PRIDE whose additional features are neededto adapt the ELF for the uses originally discussed.",{"_31":7997,"_33":7998},[],{"_35":160,"_37":7999,"_39":598,"_41":8000,"_66":8001,"_68":8002,"_70":69},"eQoeI8qL",{},[],"By assigning entries to lists, the ELF may be used as a glorified card file, with separate lists used for categories, trails, etc. This permits extensive cross-indexing by the assignment of one entry to different lists. It permits subsets and sub-sequences for any use to be held apart and examined without disturbing the lists from which they have been drawn, by copying them onto other, new lists. The ELF permits the filing of historical trails or associative (Bush) trails through documents, business correspondence, belles-lettres, case law, treaties, scholarly fields and history, and the mixture of trail with categorical filing.",{"_31":8004,"_33":8005},[],{"_35":160,"_37":8006,"_39":598,"_41":8007,"_66":8008,"_68":8009,"_70":69},"wMrr4E4J",{},[],"These are the simple uses; the compound uses are much more interesting. But since we cannot intuitively fit every possible conceptual relationship into zippered lists, imaginative use is necessary. Remember that there is no correct way to use the system. Given its structure, the user may figure out any method useful to him. A number of different arrangements can be constructed in the ELF, using only the basic elements of entry, list and link. Zippered lists may be assembled into rectangular arrays, lattices and more intricate configurations. These assemblies of lists may be assigned meaning in combination by the user, and the system will permit them to be stored, displayed, taken apart for examination, and corrected, updated, or modified.",{"_31":8011,"_33":8012},[],{"_35":160,"_37":8013,"_39":598,"_41":8014,"_66":8015,"_68":8016,"_70":69},"pFt1VreJ",{},[],"By using such combining arrangements on lists composed of text, the file can be self-documenting, with all labelling and documentation kept integrally within the file structure. It is thus possible to incorporate, in a body of information filed in the ELF, various levels of index, summary, explanation, and commentary. Many useful ways of listing and linking such documentation are possible. In Figure 3 we see some of the ways that documentary lists may be linked together. The lists shown are outline, suboutline, draft, subdraft, summary, commentary and source list. These are not all the possible types of documentary lists; for example, \"footnotes\" are omitted. The ELF will permit any number of these documentary lists; for example, \"footnotes\" are omitted. The ELF will permit any number of these documentary lists; observe that they can be built on one another, and indefinitely compounded. The system will have no trouble accepting a commentary on a commentary on a subdraft of an outline for a variant list of source materials.",{"_31":8018,"_33":8019},[],{"_35":160,"_37":8020,"_39":598,"_41":8021,"_66":8022,"_68":8023,"_70":69},"x3-LQR8L",{},[],"Figure 3 shows also how two lists may contain some of the same entries. The dashed line represents linkage between entries, the solid line shows that both lists contain the same entry. This may be useful for creating alternate versions, or, as in this example, the lists containing the same entry may have different purposes. Here, for instance, an entry in the summary is also to be found in the main draft.",{"_31":8025,"_33":8026},[],{"_35":160,"_37":8027,"_39":598,"_41":8028,"_66":8029,"_68":8030,"_70":69},"jkhhaXSF",{},[],"This self-documentation feature permits any string of text in the ELF, long or short, to be annotated or footnoted for scholarly or other purposes. Such marginalia can be temporary or permanent, for the private memoranda of an individual or for communication among different persons using the file.",{"_31":8032,"_33":8033},[],{"_35":160,"_37":8034,"_39":598,"_41":8035,"_66":8036,"_68":8037,"_70":69},"8kqVAFAr",{},[],"In a like manner, the ELF is capable of storing many texts in parallel, if they are equivalent or linked in some way. For example, instruction manuals for different models o~ the same machine may be kept in the file as linked lists, and referred to when machines are to be compared, used or fixed. This is of special use to repairmen, project managers and technical writers.",{"_31":8039,"_33":8040},[],{"_35":160,"_37":8041,"_39":598,"_41":8042,"_66":8043,"_68":8044,"_70":69},"iPRWTGod",{},[],"Moreover, the ELF's cross-sequencing feature -- the fact that links ignore permutations-- permits the collation of very different cognate textual materials for comparison and understanding. In law, this would help in comparing statutes (or whole legal systems); in literature, variorum editions and parodies. Thus such bodies as the Interpreter's Bible and a Total Shakespeare (incorporating Folios, bowdlerizations, satires and all critical commentary) could be assembled for study.",{"_31":8046,"_33":8047},[],{"_35":160,"_37":8048,"_39":598,"_41":8049,"_66":8050,"_68":8051,"_70":69},"VemIZRIl",{},[],"Let me try to illustrate the possible comprehensiveness and versatility of this file structure as applied to texts. Figure 4 shows the different arrangements that might be used by one man-- in this case an historian writing a book-- to assemble and integrate his intellectual and professional concerns. Although it is impossible to show the links between all the separate entries of these lists-- the entries are not themselves discernible in this drawing-- it is possible to note the kinds of links between lists. A thin line between lists shows that some links exist; a solid line indicates that some entries of both lists are the same.",{"_31":8053,"_33":8054},[],{"_35":160,"_37":8055,"_39":598,"_41":8056,"_66":8057,"_68":8058,"_70":69},"yydedsEL",{},[],"Perhaps this looks complicated. In fact, each of the connectors shows an indexing of one body of information to another; this user may query his file in any direction along these links, and look up the parts of one list which are related to parts of another. Therefore the lines mean knowledge and order. Note that in such uses it is the man's job to draw the connections, not the machine's. The machine is a repository and not a judge.",{"_31":8060,"_33":8061},[],{"_35":160,"_37":8062,"_39":598,"_41":8063,"_66":8064,"_68":8065,"_70":69},"OhPz96nj",{},[],"The ELF may be an aid to the mind in creative tasks, allowing the user to compare arrangements and alternatives with some prior ideal. This is helpful in planning nonlinear assemblages (museum exhibits, casting for a play,) or linear constructions of any kind. Such linear constructions include not only written texts; they can be any complicated sequences of things, such as motion pictures (in the editing stage) and computer programs.",{"_31":8067,"_33":8068},[],{"_35":160,"_37":8069,"_39":598,"_41":8070,"_66":8071,"_68":8072,"_70":69},"HHYmHWsn",{},[],"Indeed, computer programming with an on-line display and the ELF would have a number of advantages. Instructions might be interleaved indefinitely without resorting to tiny writing. Moreover, the programmer could keep up work on several variant approaches and versions at the same time and easily document their overall features, their relations to one another, and their corresponding parts. Adding a load-and-go compiler would create a self-documenting programming scratchpad.",{"_31":8074,"_33":8075},[],{"_35":160,"_37":8076,"_39":598,"_41":8077,"_66":8078,"_68":8079,"_70":69},"_590ZS8G",{},[],"The natural shape of information, too, may call for the ELF. For instance, sections of information often arrange themselves naturally in a lattice structure, whose strands need to be separately examined, pondered, or tested. Such lattices include PERT networks, programmed instruction sequences, history books and genealogical records. (The ELF can handle genealogical source documentation and its original text as well.) Indeed, any informational networks that require storage, handling and consideration will fit the ELF; a feature that could have applications in plant layout, social psychology, contingency planning, circuit design and itineraries.",{"_31":8081,"_33":8082},[],{"_35":160,"_37":8083,"_39":598,"_41":8084,"_66":8085,"_68":8086,"_70":69},"OEQFuxB_",{},[],"The ELF may, through its mutability:, its expansibility, and its self-documentation features, aid in the integration, understanding and channeling of ideas and problems that will not yield to ordinary analysis or customary reductions; for instance, the contingencies of planning, which are only partially Boolean. Often the reason for a so-called Grand Strategy in a setting is that we cannot keep track of the interrelations of particular contingencies. The ELF could help us understand the interrelations of possibilities, consequences, and strategic options. In a logically similar case, evaluating espionage, it might help trace consistencies and contradictions among reports from different spies.",{"_31":8088,"_33":8089},[],{"_35":160,"_37":8090,"_39":598,"_41":8091,"_66":8092,"_68":8093,"_70":69},"7Oik1zcC",{},[],"The use of an ELF as the basis for a management information system is not inconceivable. Its evolutionary capability would provide a smooth transition from the prior systems, phasing out old paperwork forms and information channels piecemeal. Beginning with conventional accounting arrays and information flow, and moving through discrete evolutionary steps, the ELF might help restructure an entire corporate system. Numerical subroutining could permit the system to encompass all bookkeeping. The addresses of all transaction papers, zippered to lists of their dates and contents, would aid in controlling shipments, inventory and cash. The ELF's cross-sequencing feature could be put to concrete uses, helping to rearrange warehouses (and the company library) by directing the printout of new labels to guide physical rearrangement. Inventories, property numbers and patents could be so catalogued and recatalogued in the ELF. Legal documents, correspondence, company facts and history could be indexed or filed in historical and category trails. And upper management could add private annotations to the public statements, reports and research of both the organization and its competitors, with amendments, qualifications, and inside dope.",{"_35":870,"_37":8095,"_39":598,"_41":8096,"_66":8097,"_68":8098,"_70":69},"XSAedf3j",{},[],"USES",{"_31":8100,"_33":8164},[8101,8108,8115,8122,8129,8136,8143,8150,8157],{"_31":8102,"_33":8103},[],{"_35":160,"_37":8104,"_39":598,"_41":8105,"_66":8106,"_68":8107,"_70":69},"TBpgvqZU",{},[],"While the ELF as described is expected to be general and useful, the original purposes described at the beginning of this paper call for certain further provisions. Now I would like to describe a desirable file and information handling language that will meet these needs, called the PRIDE (Personalized Retrieval, Indexing, and Documentation Evolutionary) System. Its purpose is to facilitate the use of an ELF. The system described is not yet implemented, nor even fully specified, but let us speak as though it is.",{"_31":8109,"_33":8110},[],{"_35":160,"_37":8111,"_39":598,"_41":8112,"_66":8113,"_68":8114,"_70":69},"YoLOJacw",{},[],"PRIDE includes the ELF operations. However, for safety and convenience nearly every operation has an inverse. The u~er must be permitted, given a list of what he has done recently, to undo it. It: follows that \"destroy\" instructions must fail safe; if given accidentally, they are to be revocable. For safety's sake, it should take several steps to throw a thing away completely. An important option would permit the user to retrace chronologically everything he does on the system.",{"_31":8116,"_33":8117},[],{"_35":160,"_37":8118,"_39":598,"_41":8119,"_66":8120,"_68":8121,"_70":69},"TtfDmblP",{},[],"Most of PRIDE's applications will involve text handling, either as a primary purpose or in the documentation of some other task. Hence a number of features exist for convenient text usage. Text handling con~ands (for modifying entries) include the equivalents of standard proofreader's marks for insertion, deletion and switching of sections.",{"_31":8123,"_33":8124},[],{"_35":160,"_37":8125,"_39":598,"_41":8126,"_66":8127,"_68":8128,"_70":69},"-YiOzFVh",{},[],"Also for text usage and user comfort, there are certain system non-restrictions. There is no practical restriction on the length of an input entry, and it need follow only the most trivial format conventions. In addition, the machine will interrupt any other PRIDE function to receive input text (inspiration mode). It is necessary that entries of unspecified length be acceptable to the system without fuss or warning. PRIDE does not stipulate fixed record lengths, either for input or storage; any such restrictions would have a psychologically cramping effect. There is no reason the system cannot appear to the user to have no fixed or standard unit lengths; the machine's operating units and sections should not concern him.",{"_31":8130,"_33":8131},[],{"_35":160,"_37":8132,"_39":598,"_41":8133,"_66":8134,"_68":8135,"_70":69},"f1ka6_yC",{},[],"Ideally, neither the length of entries, the number of lists, or any other parameter of a file is restricted by anything but the absolute size of all memory. This is a difficult requirement for the progra~ner. Routinely, however, the system should be able to accept entries thousands of characters long, accept hundreds of entries to a list, and accept hundreds of lists in the file. Otherwise, extraneous consideration by the user of whether there's room to add material or try out an offshoot begins to interfere with the system's use.",{"_31":8137,"_33":8138},[],{"_35":160,"_37":8139,"_39":598,"_41":8140,"_66":8141,"_68":8142,"_70":69},"rn5-scNj",{},[],"Although I have avoided discussing the means by which the user sees his file, PRIDE must, of course, have functions and con~nands for .this purpose. For a CRT these include quick lookup schemes 19, preferably with moving menus and means of readily changing the hierarchy of lookup structure; as well as visual cuing and mnemonic formats, including cursor maneuvers, overlays and animated wipes and other transitions. But such glamorous features do not reduce the challenge or worth of working through a line printer, or seeking to make the system useful under a batchprocessing monitor.",{"_31":8144,"_33":8145},[],{"_35":160,"_37":8146,"_39":598,"_41":8147,"_66":8148,"_68":8149,"_70":69},"-JZgp06o",{},[],"Many instructions aside from those already mentioned will be needed by the user; particular applications will require such operations as text lookup and integer arithmetic. And surely all the uses of the system have not been anticipated. Hence a subroutining facility is to be available, reaching to assembly language or opening into the machine's other languages. This could be used for processing the file's contents (e.g., numbers or character strings), or for creating more convenient combined operations out of the different operations dealing with file structure, input-output and text.",{"_31":8151,"_33":8152},[],{"_35":160,"_37":8153,"_39":598,"_41":8154,"_66":8155,"_68":8156,"_70":69},"fEtgYW0R",{},[],"PRIDE is one possible way to make an ELF, or any evolutionary file structure, useful. PRIDE would be a foreground, free-standing language with the primary mission of handling files and manuscripts, as discussed at the beginning, and secondary applications in ordering and documenting other kinds of complex information. Its major use would presumably be in connection with time-shared display and information systems. But such a language is only one suggestion. Actually, there is not much reason that the ELF could not be made a standard file structure for all purposes; unused capabilities would not intrude, but would still be there if unexpectedly wanted. ELF systems could be built into the file capabilities of general utility software. The actual computation involved is relatively trivial, and the ELF could easily be incorporated into I/O routines or data channel languages. Even small-scale hardware implementations are not unthinkable; a control box between a typewriter and a tape recorder, for instance.",{"_31":8158,"_33":8159},[],{"_35":160,"_37":8160,"_39":598,"_41":8161,"_66":8162,"_68":8163,"_70":69},"ywOhpk9X",{},[],"All these applications depend, of course, on the system being actually useful, which is an empirical question. A number of possible applications have been mentioned. But, except as a crutch to man's fallible mind, is there any reason to suppose that the system has any general applicability in principle?",{"_35":870,"_37":8165,"_39":598,"_41":8166,"_66":8167,"_68":8168,"_70":69},"MMUingMw",{},[],"PRIDE",{"_31":8170,"_33":8234},[8171,8178,8185,8192,8199,8206,8213,8220,8227],{"_31":8172,"_33":8173},[],{"_35":160,"_37":8174,"_39":598,"_41":8175,"_66":8176,"_68":8177,"_70":69},"6MUUElO9",{},[],"As \"philosophy\" I want to speak of two major things. First, complex file structures (like the ELF) make possible the creation of complex and significant new mediam, the hypertext and hyperfilm. Second, evolutionary file structures (like the ELF) make it possible to keep track of things that have been changing, without our awareness, all along. These include the major categories of hu, mn thought, which will go on changing.",{"_31":8179,"_33":8180},[],{"_35":160,"_37":8181,"_39":598,"_41":8182,"_66":8183,"_68":8184,"_70":69},"ZVD9A80k",{},[],"Systems of paper have grave limitations for either organizing or presenting ideas. A book is never perfectly suited to the reader; one reader is bored, another confused by the same pages. No system of paper-- book or programmed text-- can adapt very far to the interests or needs of a particular reader or student.",{"_31":8186,"_33":8187},[],{"_35":160,"_37":8188,"_39":598,"_41":8189,"_66":8190,"_68":8191,"_70":69},"CWsgnyzh",{},[],"However, with the computer-driven display and mass memory, it has become possible to create a new, readable medium, for education and enjoyment, that will let the reader find his level, suit his taste, and find the parts that take on special meaning for him, as instruction or entertainment.",{"_31":8193,"_33":8194},[],{"_35":160,"_37":8195,"_39":598,"_41":8196,"_66":8197,"_68":8198,"_70":69},"SY02UKTx",{},[],"Let me introduce the word \"hypertext\"**** to mean a body of written or pictorial material interconnected in such a complex way that it could not conveniently be presented or represented on paper. It may contain summaries or maps of its contents and their interrelations; it may contain annotations, additions, and footnotes from scholars who have examined it. Let me suggest that such an object and system, properly designed and administered, could have great potential for education, increasing the student's range of choices, his sense of freedom, his motivation, and his intellectual grasp*****. Such a system could grow indefinitely, gradually including more and more of the ~rld's written knowledge. However, its internal file structure would have to be built to accept growth, change and complex informational arrangements. The ELF is such a file structure.",{"_31":8200,"_33":8201},[],{"_35":160,"_37":8202,"_39":598,"_41":8203,"_66":8204,"_68":8205,"_70":69},"Y_K24imU",{},[],"Films, sound recordings, and video recordings are also linear strings, basically for mechanical reasons. But these, too, can now be arranged as non-linear systems-- for instance, lattices-- for editing purposes or for display with different emphasis. (This would naturally require computer control, using the ELF or a related system, and various cartridge or re-recording devices.) The hyperfilm-- a browsable or vari-sequenced movie-- is only one of the possible hypermedia that require our attention.",{"_31":8207,"_33":8208},[],{"_35":160,"_37":8209,"_39":598,"_41":8210,"_66":8211,"_68":8212,"_70":69},"ZgtLROtX",{},[],"So much for what we can create afresh with this structure. What about the things that have already been around awhile?",{"_31":8214,"_33":8215},[],{"_35":160,"_37":8216,"_39":598,"_41":8217,"_66":8218,"_68":8219,"_70":69},"MK0ffiAX",{},[],"The physical universe is not all that decays. So do abstractions and categories. Human ideas, science, scholarship and language are constantly collapsing and unfolding. Any field, and the corpus of all fields, is a bundle of relationships subject to all kinds of twists, inversions, involutions and rearrangement: these changes are frequent but unpredictable. Recall that computers, once a branch of mathematics, are now their own field (but the development of fluid logic indicates a possible merger with the art of wind instruments). Social relations, psycholinguistics and psychonomics are new fields, even though they rest on no special discoveries; political economy, natural history and social ethics are gone. Within a given area, too, the subheadings of importance are in constant flux. In the social sciences, for instance, the topic headings of the nineteen-thirties now sound quaint.",{"_31":8221,"_33":8222},[],{"_35":160,"_37":8223,"_39":598,"_41":8224,"_66":8225,"_68":8226,"_70":69},"F6SoEoFA",{},[],"While the disappearance and up-ending of categories and subjects may be erratic,, it never stops; and the meaning of this for information retrieval should be clear. Last week's categories, perhaps last night's field, may be gone today. To the extent that information retrieval is concerned with seeking true or ideal or permanent codes and categories-- and even the most sophisticated \"role indicator\" syntaxes are a form of this endeavor-- to this extent, information retrieval seems to me to be fundamentally mistaken. The categories are chimerical (or temporal) and our categorization systems must evolve as they do. Information systems must have built in the capacity to accept the new categorization systems as they evolve from, or outside, the framework of the old. Not just the new material, but the capacity for new arrangements and indefinite rearrangements of the old, must be possible. In this light, the ELF, indefinitely revisible and unperturbed by changes in overall structural relations, offers some promise.",{"_31":8228,"_33":8229},[],{"_35":160,"_37":8230,"_39":598,"_41":8231,"_66":8232,"_68":8233,"_70":69},"TSbSSVkZ",{},[],"There is, then, a general rationale. I believe that such a system as the ELF actually ties in better than anything previously used with the actual processes by which thought is progressively organized, whether into stories or hypertext or library categories. Thus it may help integrate, for human understanding, bodies of material so diversely connected that they could not be untangled by the unaided mind. For both logistic and psychological reasons it should be an important adjunct to imaginative, integrating and creative enterprises. It is useful where relationships are unclear; where contingencies and tasks are undefined and unpredictable; where the structures or final outcome it must represent are not yet folly known; where we do not know the file's ultimate arrangement; where we do not know what parts of the file are most important; or where things are in permanent and unpredictable flux. Perhaps this includes more places than we think. And perhaps here, as in biology, the only ultimate structure is change itself.",{"_35":870,"_37":8235,"_39":598,"_41":8236,"_66":8237,"_68":8238,"_70":69},"W1agzarw",{},[],"Philosophy",{"_31":8240,"_33":8304},[8241,8248,8255,8262,8269,8276,8283,8290,8297],{"_31":8242,"_33":8243},[],{"_35":160,"_37":8244,"_39":598,"_41":8245,"_66":8246,"_68":8247,"_70":69},"vil6PfRd",{},[],"This paper has proposed a different kind of structure for handling information.",{"_31":8249,"_33":8250},[],{"_35":160,"_37":8251,"_39":598,"_41":8252,"_66":8253,"_68":8254,"_70":69},"euNs9O4g",{},[],"Essentially it is a file with certain storage provisions which, combined, permit the file's contents to be arranged any-which-way, and in any number of ways at once. A set of manipulation functions permits making changes or keeping track of developments. The file is capable of maintaining many different arrangements at the same time, many of which may be dormant. This makes ordinary measures of efficiency inappropriate; as with high fidelity music systems, enrichment is derived from the lavish use of surplus capacity.",{"_31":8256,"_33":8257},[],{"_35":160,"_37":8258,"_39":598,"_41":8259,"_66":8260,"_68":8261,"_70":69},"r-nXVNgr",{},[],"The key ideas of the system are the inter-linking of different lists, regardless of sequence or additions; the re-configurable character of a list complex into any humanly conceivable forms; and the ability to make copies of a whole list, or list complex-- in proliferation, at will-- to record its sequence, contents or arrangement at a given moment. The Evolutionary List File is a member of the class of evolutionary file structures; and its particular advantages are thought to be psychological, not technical. Despite this file's adaptability to complex purposes, it has the advantage of being conceptually very simple. Its structure is complete, closed, and unified as a concept. This is its psychological virtue. Its use can be easily taught to people who do not understand computers. We can use it to try out combinations that interest us, to make alternatives clear in their details and relationships, to keep track of developments as they occur, to sketch things we know, like, or currently require, and it will stand by for modifications. It can be extended for all sorts of purposes, and implemented or incorporated in any programming language.",{"_31":8263,"_33":8264},[],{"_35":160,"_37":8265,"_39":598,"_41":8266,"_66":8267,"_68":8268,"_70":69},"VvNgCVZ8",{},[],"There are probably various possible file structures that will be useful in aiding creative thought. This one operates, as it were, on lists that hook together sideways, and their copies. There may be many more.",{"_31":8270,"_33":8271},[],{"_35":160,"_37":8272,"_39":598,"_41":8273,"_66":8274,"_68":8275,"_70":69},"utmMKr14",{},[],"* The Bush Rapid Selector 2 is a powerful microfilm instrument, but it is not suited to idiosyncratic personal uses, nor to evolutionary modification, as described.",{"_31":8277,"_33":8278},[],{"_35":160,"_37":8279,"_39":598,"_41":8280,"_66":8281,"_68":8282,"_70":69},"qvdApsCp",{},[],"** It is believed that this account is reasonably correct for such writers as Tolstoy, Winston Churchill and Katherine Anne Porter. Those who can adhere to a prior outline faithfully, like James Fenimore Cooper, tend to be either hacks or prodigres, and do not need this system",{"_31":8284,"_33":8285},[],{"_35":160,"_37":8286,"_39":598,"_41":8287,"_66":8288,"_68":8289,"_70":69},"J20Hgxnh",{},[],"*** For a poignant, mordant portrayal of the writer's struggle, the reader is directed to Gorey's \"The Unstrung Harp\", or \"Mr Earbass Writer.s a Novel\".",{"_31":8291,"_33":8292},[],{"_35":160,"_37":8293,"_39":598,"_41":8294,"_66":8295,"_68":8296,"_70":69},"VagoetmH",{},[],"**** An ELF might even be constructed out of cards, blocks, sticks, and strings using techniques of puppetry, but this would not be a convenient object.",{"_31":8298,"_33":8299},[],{"_35":160,"_37":8300,"_39":598,"_41":8301,"_66":8302,"_68":8303,"_70":69},"QbGf8Nlp",{},[],"***** The sense of \"hyper-\" used here connotes extension and generality; cf. \"hyperspace.\" The criterion for this prefix is the inability of these objects to be comprised sensibly into linear media, like the text string, or even media of somewhat higher complexity. The ELF is a hyperfile.",{"_35":870,"_37":8305,"_39":598,"_41":8306,"_66":8307,"_68":8308,"_70":69},"m0CwQfuY",{},[],"CONCLUSION",{"_31":8310,"_33":8444},[8311,8318,8325,8332,8339,8346,8353,8360,8367,8374,8381,8388,8395,8402,8409,8416,8423,8430,8437],{"_31":8312,"_33":8313},[],{"_35":160,"_37":8314,"_39":598,"_41":8315,"_66":8316,"_68":8317,"_70":69},"nbc06OEu",{},[],"Bush, V., \"As We May Think.\" :['he Atlantic Monthly, p. 101-108; July, 1945.",{"_31":8319,"_33":8320},[],{"_35":160,"_37":8321,"_39":598,"_41":8322,"_66":8323,"_68":8324,"_70":69},"gvbiK-6J",{},[],"Hirsch, P., \"The Bush :Ropid Selector.\" Datamation, p. 56-57; June, 1965.",{"_31":8326,"_33":8327},[],{"_35":160,"_37":8328,"_39":598,"_41":8329,"_66":8330,"_68":8331,"_70":69},"2kidwpb4",{},[],"Wallace, E. M., \"Experience with EDP Support of Individuals' File Maintenance.\" Parameters of Information Science: Proceedings of the American. Documentotion Institute (American Documentation Institute), p. 259-261; 1/1964.",{"_31":8333,"_33":8334},[],{"_35":160,"_37":8335,"_39":598,"_41":8336,"_66":8337,"_68":8338,"_70":69},"brjllhDj",{},[],"Gorey, E., \"The Unstrung Harp; or, Mr. Earbrass Writes a Novel,\" Duell, Sloan and Pearce, N. Y.; 1953.",{"_31":8340,"_33":8341},[],{"_35":160,"_37":8342,"_39":598,"_41":8343,"_66":8344,"_68":8345,"_70":69},"j6DZ_V0z",{},[],"IBM Data Processing Division, \"The IBM Administrative Terminal System,\" Brochure 520-1146.",{"_31":8347,"_33":8348},[],{"_35":160,"_37":8349,"_39":598,"_41":8350,"_66":8351,"_68":8352,"_70":69},"Elv4c1-7",{},[],"IBM Technical Publications Department, \"14~0/1460 Administrative Terminal System Application Description,\" White Plains, New York.",{"_31":8354,"_33":8355},[],{"_35":160,"_37":8356,"_39":598,"_41":8357,"_66":8358,"_68":8359,"_70":69},"VXgj2HKv",{},[],"Timberlake, W. D., \"Administrative Terminal System\" (abstract.) STWP Proceedings; May, 1965.",{"_31":8361,"_33":8362},[],{"_35":160,"_37":8363,"_39":598,"_41":8364,"_66":8365,"_68":8366,"_70":69},"sweYTw0R",{},[],"Farrell, A. C., \"Evolution of Automated Writing.\" STWP Proceedings; May, 1965.",{"_31":8368,"_33":8369},[],{"_35":160,"_37":8370,"_39":598,"_41":8371,"_66":8372,"_68":8373,"_70":69},"-MYkGB9e",{},[],"Bobrow, D. G., and Bertram, R., \"A Comparison of ListProcessing Languages.\" Comm. ACM, p. 231-240; April, 1964.",{"_31":8375,"_33":8376},[],{"_35":160,"_37":8377,"_39":598,"_41":8378,"_66":8379,"_68":8380,"_70":69},"-BMvkrba",{},[],"Comfort, W. T., \"Multiword List Items.\" Comm. ACM, p. 357-362; June, 1964.",{"_31":8382,"_33":8383},[],{"_35":160,"_37":8384,"_39":598,"_41":8385,"_66":8386,"_68":8387,"_70":69},"zhPgIVOa",{},[],"Weizenbaum, J., \"Knotted List Structures.\" Comm. ACM, p. 161-165; Mar., 1962.",{"_31":8389,"_33":8390},[],{"_35":160,"_37":8391,"_39":598,"_41":8392,"_66":8393,"_68":8394,"_70":69},"OIfPmIuo",{},[],"Prywes, N. S,, and Gray, H. J., \"The Multilist System for Real Time Storage and Retrieval,\" Proceedings of IFIP Conference, p. 112-116; 1962.",{"_31":8396,"_33":8397},[],{"_35":160,"_37":8398,"_39":598,"_41":8399,"_66":8400,"_68":8401,"_70":69},"6DBy3V5o",{},[],"Prywes, N. S., \"Interim Technical Report: The Organization of Files for Command and Control,\" Moore School o[ Engineering; March, 1964.",{"_31":8403,"_33":8404},[],{"_35":160,"_37":8405,"_39":598,"_41":8406,"_66":8407,"_68":8408,"_70":69},"noLe9wK8",{},[],"Bachman, C. W., and Williams, S. B., \"The Integrated Data Store--A General Purpose Programming System for Random Access Memories,\" AFIPS Conference Proceedings, p. 411-422; 1964.",{"_31":8410,"_33":8411},[],{"_35":160,"_37":8412,"_39":598,"_41":8413,"_66":8414,"_68":8415,"_70":69},"W4FVfs-l",{},[],"General Electric Computer Department, \"I-D-S:\" Company Brochure CPB-425.",{"_31":8417,"_33":8418},[],{"_35":160,"_37":8419,"_39":598,"_41":8420,"_66":8421,"_68":8422,"_70":69},"R9miEYK9",{},[],"General Electric Computer Department, \"Introduction to Integrated Data Store,\" Company Brochure CPB-1048; 1965.",{"_31":8424,"_33":8425},[],{"_35":160,"_37":8426,"_39":598,"_41":8427,"_66":8428,"_68":8429,"_70":69},"6y6dvbQc",{},[],"Bachman, C. W., \"Software for Random Access Processing,\" Datamation; April, 1965.",{"_31":8431,"_33":8432},[],{"_35":160,"_37":8433,"_39":598,"_41":8434,"_66":8435,"_68":8436,"_70":69},"s7sj3fqn",{},[],"General Electric Computer Department, \"Integrated Data Store: New General Electric Technique for Organizing Business Data\"; January, 1965",{"_31":8438,"_33":8439},[],{"_35":160,"_37":8440,"_39":598,"_41":8441,"_66":8442,"_68":8443,"_70":69},"dN4rcSg2",{},[],"Corbin, H. S., and Stock, G. J., \"On-Line Querying via a Display Console,\" Fourth National Symposium on Information Display: Technical Session Proceedings, p. 127-154; 1964",{"_35":870,"_37":8445,"_39":598,"_41":8446,"_66":8447,"_68":3495,"_70":69},"uqI6a1JS",{"_273":2113},[],{"_31":8449,"_33":8482},[8450,8458,8466,8474],{"_31":8451,"_33":8452},[],{"_35":1875,"_37":8453,"_39":598,"_41":8454,"_66":8455,"_68":8456,"_70":8457},"NgIj3tuB",{"_273":323},[],"FIGURE 1 -- Zippered lists: l-for-1 links between entries are invariant under list permutation. ","ipfs://bafkreibl7ifcpyr67u4olo4ohic32kko7x5gato4nlmw7j5xlnwprpcad4",{"_31":8459,"_33":8460},[],{"_35":1875,"_37":8461,"_39":598,"_41":8462,"_66":8463,"_68":8464,"_70":8465},"CdTbIhWM",{"_273":323},[],"FIGURE 2 -- Spinoff of variants: extra versions need little space. ","ipfs://bafkreiadfa7mmsdz53qmhvby672bnwtycms3owbqddu4xqpe7pnkepi7a4",{"_31":8467,"_33":8468},[],{"_35":1875,"_37":8469,"_39":598,"_41":8470,"_66":8471,"_68":8472,"_70":8473},"q8vrVFNn",{"_273":323},[],"FIGURE 3 -- All levels of documentation in the ELF. ","ipfs://bafkreig5gzkizxsjzlsmc3b3poojhl4jqdnglfwedrmwl7q7ilssautoku",{"_31":8475,"_33":8476},[],{"_35":1875,"_37":8477,"_39":598,"_41":8478,"_66":8479,"_68":8480,"_70":8481},"m19q9xbJ",{"_273":323},[],"FIGURE 4 -- ELF's capacity for total filing: hypothetical use by historian. Thin lines indicate links; heavy rules indicate some of same entries. ","ipfs://bafybeicytkj5rhjnrnuuitmhp22z5merjfagbnsgyylu67j25655mod2ii",{"_35":870,"_37":8483,"_39":598,"_41":8484,"_66":8485,"_68":8486,"_70":69},"hfbOZDKK",{},[],"Figures",[53],"/records/42-a-file-structure-for-the-complex-the-charging-and-the-indeterminate",{"_82":613},{},{"_37":595,"_95":53,"_54":8492,"_71":598,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,597],1772031973355,[149,595,598],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/42-a-file-structure-for-the-complex-the-charging-and-the-indeterminate\",\"bafy2bzacedycyq4lxmpja5dwroz5tgu5jkjckbpthslber6ultftqv4ftg22s\"]",{"_110":8497,"_147":8788,"_150":8789},{"_112":8498,"_131":132,"_133":8787,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":8499,"_37":8785},{"_28":8500,"_71":619,"_72":53,"_73":8781,"_54":8782,"_76":626,"_78":626,"_80":8783,"_84":8784,"_86":619,"_88":89},[8501,8508,8515,8522,8533,8546,8749],{"_31":8502,"_33":8503},[],{"_35":160,"_37":8504,"_39":619,"_41":8505,"_66":8506,"_68":8507,"_70":69},"20cy6VeO",{},[],"A Critique",{"_31":8509,"_33":8510},[],{"_35":160,"_37":8511,"_39":619,"_41":8512,"_66":8513,"_68":8514,"_70":69},"sQLsV_Z-",{},[],"Jef Raskin",{"_31":8516,"_33":8517},[],{"_35":160,"_37":8518,"_39":619,"_41":8519,"_66":8520,"_68":8521,"_70":69},"Z2xKDFDU",{},[],"Information Appliance 1014 Hamilton Court Menlo Park, CA 94025",{"_31":8523,"_33":8524},[],{"_35":8525,"_37":8526,"_39":619,"_41":8527,"_66":8531,"_68":69,"_70":8532},"File","fCVdbVO9",{"_8528":8529,"_82":8530},"size",609579,"317426.317449.pdf",[],"ipfs://bafybeibpfopsn2zgzrvgglv4rgvkt34qq4crmkr3xysybv2mhe44jxlnai",{"_31":8534,"_33":8542},[8535],{"_31":8536,"_33":8537},[],{"_35":160,"_37":8538,"_39":619,"_41":8539,"_66":8540,"_68":8541,"_70":69},"4cDicjfV",{},[],"Hypertext has received a lot of mostly uncritical attention. The author sees it as one part inspiration and nine parts hyperbole. A number of user interface and technical problems are discussed.",{"_35":870,"_37":8543,"_39":619,"_41":8544,"_66":8545,"_68":5873,"_70":69},"a_-1R5YL",{},[],{"_31":8547,"_33":8744},[8548,8555,8562,8569,8576,8583,8590,8597,8604,8611,8618,8625,8632,8639,8646,8653,8660,8667,8674,8681,8688,8695,8702,8709,8716,8723,8730,8737],{"_31":8549,"_33":8550},[],{"_35":160,"_37":8551,"_39":619,"_41":8552,"_66":8553,"_68":8554,"_70":69},"6Ps5RA_N",{},[],"The literature on Hypertext is generally effusive and non-critical. Even Conklin’s survey article in Computer (IEEE Computer, September 1987, pg 17 ff) ends up admitting that the author hopes that “the reader come away from this article excited, eager to try using hypertext for himself, and aware that he is at the beginning of something big, something like the invention of the wheel, but something that still has enough rough edges that no one is really sure that it w-ill fulfill its promise.” This article looks at what some have seen as rough edges but which may be cracks that extend deep into the heart of hypertext.",{"_31":8556,"_33":8557},[],{"_35":160,"_37":8558,"_39":619,"_41":8559,"_66":8560,"_68":8561,"_70":69},"lBb_qwuZ",{},[],"Conklin’s advocacy is tame stuff compared with Hypertext’s prime mover, Ted Nelson, who writes with the messianic verve characteristic of visionaries. Many followers and supporters of the Hypertext concept take much the same tone; in fact, there have not been many who have gainsaid the concept,for on the surface it seems a good one that is well within our technical reach. On the other hand, it has not been implemented except for a few more or less experimental projects: the grand vision languishes unfinished, though often started. If the details are kept fuzzy enough, Hypertext seems like a wonderful, universally applicable, powerful, natural, human-oriented model for organizing and accessingknowledge. Having felt that draw, and also havingimplemented some real-world projects that were considered visionary when I started but became well-accepted (and commercially successful) when I was finished, I took a closer look at Hypertext and found some deep and fundamental difficulties that have not been much discussed.",{"_31":8563,"_33":8564},[],{"_35":160,"_37":8565,"_39":619,"_41":8566,"_66":8567,"_68":8568,"_70":69},"du1Hpm4i",{},[],"A good place to begin is with some other ideas that, like Hypertext, sound very good but are simpler, and have failed to deliver on their promise.",{"_31":8570,"_33":8571},[],{"_35":160,"_37":8572,"_39":619,"_41":8573,"_66":8574,"_68":8575,"_70":69},"ISbpLacr",{},[],"There is a certain frustration in playing adventure games. The games ostensibly avoid requiring that you learn special computer commands by allowing you to frame your commands in English. This sounds very inviting, but whenever your response varies from the stylized vocabulary and grammar that the game recognizes you run into a wall of incomprehension. The game spins off a subgame of guessing which words the developer thought useful or significant. Synonyms in English may or may not be synonyms to the game; you often find that though what you said is correct, it is not accepted. All in all these games tend to be a frustrating experience unless you come to accept that figuring just how to emasculate your vocabulary and grammar is part of the game. Not everybody thinks this is fun, but ifyou enjoy it, you are a prime example of a puzzle- lover or ‘hacker” in the old, non-pejorative sense of a person who likes to play with a system - for hours and days on end if necessary - in order to learn how it works.",{"_31":8577,"_33":8578},[],{"_35":160,"_37":8579,"_39":619,"_41":8580,"_66":8581,"_68":8582,"_70":69},"7LdIe5sx",{},[],"What is really happening in these games is that the players are learning a set of computer commands -by trial and error. In an adventure-style sword battle your knowledge of fencing is of no use, but your knowledge of the system developers’ frame of mind is. The notes that most players end up making for their own use form the manual that the game’s inventors (deliberately) didn’t provide. In other words, there is not much difference between an adventure game and a poorly documented computer program. Both present the same kind of challenge, and appeal to much the same set of users.",{"_31":8584,"_33":8585},[],{"_35":160,"_37":8586,"_39":619,"_41":8587,"_66":8588,"_68":8589,"_70":69},"Oe00S4Cw",{},[],"The problem with adventure games was that something that sounds like the right, natural, inevitable and easiest thing to do failed (in some sense) because it delivered only the aroma of what was promised. When you are hungry, this can be worse than nothing at all. The full mea1 may, in fact, be undeliverable. Natural language may be an inherently unsuitable medium for programming (in the present meaning of the word) or even controlling an imaginary universe.",{"_31":8591,"_33":8592},[],{"_35":160,"_37":8593,"_39":619,"_41":8594,"_66":8595,"_68":8596,"_70":69},"xMS9H8Z8",{},[],"This insight can be extended to Hypertext. Hypertext, in a nutshell, is text (in the sense of what one finds in books) where there are links between different texts and portions of texts for some very large universe of knowledge. You might be reading, on the display of your information appliance, about butterflies. Say that the text mentions a gathering of monarch butterflies that occurs in Monterey, California. Soyou point to (by some means) the word monarch, andyoupress the udelve deeper” button (or some such action) and a picture of the butterfly comes onto your screen. You touch one of the legs of the butterfly and up comes, say, details of the leg of the butterfly or perhaps an article on butterfly legs. You then press the ‘back to where I was”button, and continue reading. Upon pointingto the word“Califomia” the delve deeper button might give you a map of California with Monterey called out, and so forth.",{"_31":8598,"_33":8599},[],{"_35":160,"_37":8600,"_39":619,"_41":8601,"_66":8602,"_68":8603,"_70":69},"2n-jbOIu",{},[],"As technology permits, the concept of “text” in Hypertext expands to include color images, movingimages (movies), sounds, real-time links to the author or other experts on the subject you are “reading’ about, reference librarians who can point to further sources of information, and literally anything else that might conceivably be pumped through wires or the aether to your system.",{"_31":8605,"_33":8606},[],{"_35":160,"_37":8607,"_39":619,"_41":8608,"_66":8609,"_68":8610,"_70":69},"aozE_rb8",{},[],"Lastly, the Hypertext vision includes a growing body of on-line information, becoming richer as it is used because users provide an ever-increasing number of sources of data and links between items. It assumes wide acceptance by a large number of ordinary, non-technophilic people.",{"_31":8612,"_33":8613},[],{"_35":160,"_37":8614,"_39":619,"_41":8615,"_66":8616,"_68":8617,"_70":69},"NEBRLVSs",{},[],"It sounds wonderful.",{"_31":8619,"_33":8620},[],{"_35":160,"_37":8621,"_39":619,"_41":8622,"_66":8623,"_68":8624,"_70":69},"cxFHuJRl",{},[],"There are, of course, some technological questions that can be asked about Hypertext: for example, how will we get the very high bandwidths between sources of information and the individual’s machine required to make pictures and text available quickly enough to avoid frustration? Another technological problem lies in the massive storage capacity, network, switching, and software required. There are social, legal, and economic problems as well. Examples of these problems include questions such as: will the financially privileged have easier access, and thus widen the gap between haves and have nots? Nelson has addressed (though without sufficient depth) the questions of who owns the material, who owns the all-important linkages, how copyrights are preserved, who pays for the central system, how to insure compatibility between systems and how an author gets paid. But this essay is concerned with basic conceptual problems, assuming that the technological problems will be solved in the natural course of events, and leaving the other questions for another time. I will also ignore the very real but probably not as serious “chicken and eg&’ problem of how Hypertext gets started, since at first it is necessarily rather weak and thin. While this last problem will have to be faced, other services, such as telephones faced the same dilemma and overcame it. Whether it gets off the ground depends in part on the quality of the initial system: where will we get enough linked text to make it useful at first?",{"_31":8626,"_33":8627},[],{"_35":160,"_37":8628,"_39":619,"_41":8629,"_66":8630,"_68":8631,"_70":69},"wXUYYqAh",{},[],"The problem with “natural language” games, which also applies to many “natural language” interfaces for more serious (this does not imply more worthy) applications, has a parallel in the proposed Hypertext systems. As an example, take the passage where the text mentioned a gathering of monarch butterflies. First of all, not every word will have the same kind or depth of information behind it. Say that a previous user had looked up the meaning of the word Umonarch” and established a link to ‘king.” Then, when you point to umonarch” meaning a kind of butterfly, you might find yourself in the midst of a discussion of the divine rights of hereditary rulers. Yougo“up”and try“butterfly”andyoufindageneraldescription ofthelepidoptera, which does not mention “monarch” since it only gives the Latin name, which you do not recognize. You can grope around for a while, trying this and that sub-heading in what you find, and maybe what you want is there, and maybe it isn’t. One key question is: How Do You Know If It’sThere? This isn’t the advertised smooth, rapid access “feel” of hypertext, this is a fishing expedition.",{"_31":8633,"_33":8634},[],{"_35":160,"_37":8635,"_39":619,"_41":8636,"_66":8637,"_68":8638,"_70":69},"Hcvv6_TM",{},[],"Let’s say that, by some means, you can point for specificity to the whole phrase “monarch butterfly” and you get, rather than some particular linked item, a list or menu of such items and other menus. Aside from having to learn how to operate the menus and make selections from them, it is well known that menus are a slow way of getting from place to place, especially if they are many levels deep. Avoiding, also, the question ofhow (orby whom) the menus are generated (Nelson suggests that people will spontaneously create them and charge for their use), let’s say that one menu item leads you to a picture of the butterfly. As before, you point to a leg. Now, it is not clear if you are pointing to, say, the tarsus, the whole leg, to legs in general, to butterfly legs, or to the whole insect. Since butterflies are beautifully symmetrical, are you pointing to ask about symmetry in general?",{"_31":8640,"_33":8641},[],{"_35":160,"_37":8642,"_39":619,"_41":8643,"_66":8644,"_68":8645,"_70":69},"giJZc-me",{},[],"Not every item or detail in a picture will have a reference attached to it. How will you tell which do and which don’t? None of the references about Hypertext seem to carefully address this problem. I tried a medical “Hypertext” styled system a few months ago, based onvideo disks with immense storage capacity. You could point to a structure in a dissection and get a close up view, or views from other angles. It seemed fine when being demonstrated by someone who knew which body parts had further data behind them, but when I tried to use it and pointed to structures that I was curious about, most of the time the system, being finite, could give me no information.",{"_31":8647,"_33":8648},[],{"_35":160,"_37":8649,"_39":619,"_41":8650,"_66":8651,"_68":8652,"_70":69},"vOxfj08Y",{},[],"There is a vague assumption that as people use it, the system will monitor and gather up the links they generate, and thus grow in depth and value. Does a link happen whenever you move from one frame or screenful to another? It will not, according to Nelson. You will have to explicitly tell the system when you are making a link (just how you do this is not specified), and I think it is important to ask if you are likely to bother making links at all. Remember: people are inherently lazy, and when you are hot on the trail of some information how likely are you to stop and tell the system which links seem valuable to you? If as a result of this observation you make the system record all links, good and bad, will there be human editors who will prune them (and where would we get these editors, how would we pay them, and is it in principle even possible to tell a good link from a bad link?) If the links are not pruned, won’t most searches turn into wild goose chases? One man’s links are another man’s sausages.",{"_31":8654,"_33":8655},[],{"_35":160,"_37":8656,"_39":619,"_41":8657,"_66":8658,"_68":8659,"_70":69},"RrBGLYMM",{},[],"In other words, it is not clear that it can work as neatly as the hand-waving of its visionaries make it seem. I have been told that there areno bad links, and in a sense this is correct: any connection, even if it is a misreading of, say, “sheer” for “shear,” is meaningful and potentially useful (say to a person studying common reading mistakes, or to a poet). But the clutter a user faces will be enormous.",{"_31":8661,"_33":8662},[],{"_35":160,"_37":8663,"_39":619,"_41":8664,"_66":8665,"_68":8666,"_70":69},"r0h86nS-",{},[],"The central lacuna is the omission of any specification of a human interface. The Xanadu project, trying to implement a real-world version of Hypertext, is just building a central processing and storage facility. When I have asked the implementors what it will look like to the user-a central question if it is to be widely accepted, and it must be used by a large population to fulfill the plans of its inventors -they say that the “front end” is not their concern. I claim that the “front end,” namely what devices and how it will look to users is as important as the central nexus. It may be more important, since if the front end puts people off, they will never get any further. Yet there is no user interface specification for what Hypertext will look like to the individual user. It is important that the user interface be reasonably uniform from implementation to implementation. This point has been well demonstrated by the Apple Macintosh computer. One of my goals when designing the Mac was to make it easier for a software designer to use a provided interface model than to create a new one. This was a positive use of people’s laziness. Thus, unlike any previous system, you can move from application to application with relative ease, and buying a new programis not as traumatic an experience asitused tobe. With earlier computers, each new application program gave you a nearly totally new experience.",{"_31":8668,"_33":8669},[],{"_35":160,"_37":8670,"_39":619,"_41":8671,"_66":8672,"_68":8673,"_70":69},"jV0qNpZK",{},[],"A Hypertext system will have good “feel” only if it is fast enough. This is another area solved primarily by looking the other way. In ten years the word“work” may easily generate 200 pages of menus of referents (since the word “work,” like so many other words, has everything from negative imphcations (dirty work) to positive ones (work ethic), to technical ones (force times distance), to political ones (ownership of one’s labor)). How long will it take the central system to find the menus, how long will it take to transmit them, how long will it take you to go through them, how long will it take you to get to the next submenu. 3 Most people don’t use dictionaries and encyclopedias because it takes from half a minute to a few minutes to look something up. If a computer system is as slow or slower, it will be avoided as thoroughly as people avoid other reference systems.",{"_31":8675,"_33":8676},[],{"_35":160,"_37":8677,"_39":619,"_41":8678,"_66":8679,"_68":8680,"_70":69},"wHOxmRd4",{},[],"The lack of a carefully thought out “front end” is thus a major flaw in the design of Hypertext. A person should be able to use it from any available port, whether at home, at school, in the office, at the library, or when walking in the park using Alan Kay’s mythical Dynabook. (There’s another fine-sounding idea that has never been specified to the point where you can evaluate if it’s workable. It, too, lacks an interface specification and apparently does what the user intends by a combination of wishful thinking and magic.)",{"_31":8682,"_33":8683},[],{"_35":160,"_37":8684,"_39":619,"_41":8685,"_66":8686,"_68":8687,"_70":69},"_eBVbOxc",{},[],"In short, Hypertext only sounds like a good idea. It tends to evaporate when looked at closely. There are three basic human interface problems: (i) the linkages are often either cumbersome, wrong for your needs, or trivial, (ii) the problem of what aspect of a word, phrase, or picture you intend has not been addressed, (iii) a uniform and excellent human interface specification is both necessary and absent.",{"_31":8689,"_33":8690},[],{"_35":160,"_37":8691,"_39":619,"_41":8692,"_66":8693,"_68":8694,"_70":69},"_ks5UroC",{},[],"I am sure enough of human ability to believe that the problems being addressed by Hypertext- like systems are not impossible to solve. What I am questioning is whether this particular proposed part of a solution, namely linked text (with a very broad definition of “text”) is the right one, or even a feasible one. As with playing“adventure” games, you will be trying to second guess the link builder’s frame of mind rather than staying within the subject you are working with. Knowledge of the system will often be more valuable than understanding your field. As the students of a poor teacher learn to give not the right answers but those the teacher wants, Hypertext users will spend much of their time pleasing the system instead of themselves.",{"_31":8696,"_33":8697},[],{"_35":160,"_37":8698,"_39":619,"_41":8699,"_66":8700,"_68":8701,"_70":69},"nFS_NnyR",{},[],"It is perhaps worthwhile asking why Nelson and the Xanadu people have looked at the aspects they have and ignored the ones mentioned here. I hope I may be excused for making an ad hominem observation: these people consider themselves hackers (in the best sense). They feel at home at the annual Hackers’ Conference. They love technology, and like Joyce’s Leopold Bloom, thrive on innards. They can discuss the minutiae of a particular system to all hours and, I fear, sometimes confuse their satisfaction in technical ingenuity and accomplishment with usability. The power of a linked data structure is formidable and amazing. My own thesis in computer science exploited such a structure. From speaking with Xanadu’s implementors, and some people who hope to tap into its data, I have seen how they have been seduced. The potential is enormous, the attention given to implementation of searches into vast quantities of human knowledge brilliant, and a host of fascinating problems in computer science have been attacked, and some seem solved. One gets an honest feeling of accomplishment. But they have not addressed the question: when a person sits down at her system what will have to be done first? What will she see? What is the next step the user takes, and the next...? How will it look? How many keystrokes or mouse pushes or dnger jabs will it take to find what is wanted? How long will it take? No, they speak to me of megabytes and optical disks instead of Susan and Jim and Marjorie and Bill. They speak of the great benefits that will accrue to individuals - that’s one end; and the vast linked data base - that’s the other end. But when asked how the ends are made to meet, just how the natural impedence between them is overcome, the designers become inspecific and waflle. How humans interact with systems is not their field and is not really close to their hearts. It is not the computer science they studied. It is a soft subject and making good interfaces (which they fervently believe should be done) will not win them the sincerest plaudits of their peers.",{"_31":8703,"_33":8704},[],{"_35":160,"_37":8705,"_39":619,"_41":8706,"_66":8707,"_68":8708,"_70":69},"FWOV7fMg",{},[],"None of this denies their interest in doing good things for the world and for individual people. The “how” just hasn’t been thought through. This may stem from Nelson’s belief that “rhe starting point in designing a computer system must be the creation of the conceptual and psychological environment -the seeming of the system [a nice phrase, but not very informative] -what I and my associates call the ‘virtuality.“’",{"_31":8710,"_33":8711},[],{"_35":160,"_37":8712,"_39":619,"_41":8713,"_66":8714,"_68":8715,"_70":69},"xGy0fVhy",{},[],"And what everybody else calls the “concept.” I agree that one must begin by deciding, as Nelson says, “bow it ought to be.” Unfortunately, Nelson’s “how it ought to be” does not include specifics of how it works in detail. Whether the hypertext concept is useful or not is most decidedly a function of the user interface, just as computers are more or less useful depending on how they facilitate access to their power. Consider the relative di&ulty of using a double-edged razor blade without a handle. It is just as sharp, but much harder to use. Nelson’s avoidance of what he calls “front end” issues is a major failing in the quality of his vision, his priorities, and his understanding of what makes things work well for people.",{"_31":8717,"_33":8718},[],{"_35":160,"_37":8719,"_39":619,"_41":8720,"_66":8721,"_68":8722,"_70":69},"CBXbnSIC",{},[],"Since creating the Macintosh project at Apple I’ve led the design of a number of products including the Canon Cat and SwyftWare. In the process, my associates and I obtained an excellent interface between people and text by using exactly what Nelson decried: a straightfor- ward linear structure. It was acted upon not by links and list processing but by an extremely fast search (which can be considered a real-time volatile link). One major difference is that we were driven to this internal structure by starting with a particular and finely tuned human interface, and only then searching for technology to implement it. I do not agree with Nelson’s statement that people naturally think in hierarchical structures of many layers. If that assumption falls, so does most of the Hypertext concept. Studies show that people prefer flat structures over deep ones, and if we do not accede to the way humans work then we are not likely to design workable products.",{"_31":8724,"_33":8725},[],{"_35":160,"_37":8726,"_39":619,"_41":8727,"_66":8728,"_68":8729,"_70":69},"xwuvOE_7",{},[],"The Hypertext vision is worth a try. The demonstrations so far have been tantalizing. It is my guess that the reality will remain tantalizing, and will never fulfill the dreams of Hypertext’s advocates - nor the dreams that they instilled in me, for that matter.",{"_31":8731,"_33":8732},[],{"_35":160,"_37":8733,"_39":619,"_41":8734,"_66":8735,"_68":8736,"_70":69},"5GA6nFW1",{},[],"While Hypertext itself may or may not be a good idea, the vision of giving everybody access to vast reaches of human knowledge is a praiseworthy one. There are probably better and more realizable ways. Hypertext is certainly incomplete at present, both in terms of implementation (as its designers would agree) and in terms of concept (they might not agree). My intent has been to present a countervailing opinion to the vast majority of what has been written and to balance the present uncritical discussion (that is, adulation) of Hypertext.",{"_31":8738,"_33":8739},[],{"_35":160,"_37":8740,"_39":619,"_41":8741,"_66":8742,"_68":8743,"_70":69},"bbJxeQVK",{},[],"Thanks to David Alzofon, Sam Bernstein, and Scott Kim for their constructive comments.",{"_35":870,"_37":8745,"_39":619,"_41":8746,"_66":8747,"_68":8748,"_70":69},"gJdEF3e3",{},[],"A CRITIQUE",{"_31":8750,"_33":8777},[8751,8758,8770],{"_31":8752,"_33":8753},[],{"_35":160,"_37":8754,"_39":619,"_41":8755,"_66":8756,"_68":8757,"_70":69},"4GwbvGmn",{},[],"Conklin, Jeff,“Hypertext: An Introduction and Survey-, IEEE Computer, September 1987,17ff.",{"_31":8759,"_33":8760},[],{"_35":160,"_37":8761,"_39":619,"_41":8762,"_66":8763,"_68":8769,"_70":69},"M04wkaKc",{},[8764],{"_35":919,"_167":8765,"_169":8766,"_41":8768,"_70":69},[137],[8767],408,{},"Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission.",{"_31":8771,"_33":8772},[],{"_35":160,"_37":8773,"_39":619,"_41":8774,"_66":8775,"_68":8776,"_70":69},"32eHgLoA",{},[],"c 1989 ACM 089791-340-X/89/001 l/0330$1.50 330",{"_35":870,"_37":8778,"_39":619,"_41":8779,"_66":8780,"_68":7367,"_70":69},"2jkLBy9Y",{},[],[53],"/records/the-hype-in-hypertext",{"_82":635},{},{"_37":616,"_95":53,"_54":8786,"_71":619,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,618],1772031973226,[149,616,619],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/the-hype-in-hypertext\",\"bafy2bzacecxctduy6skwjksign4curadmp63aojdgrkhaiso2gvseh4usks6a\"]",{"_110":8791,"_147":9676,"_150":9677},{"_112":8792,"_131":132,"_133":9675,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":8793,"_37":9673},{"_28":8794,"_71":641,"_72":53,"_73":9669,"_54":9670,"_76":648,"_78":648,"_80":9671,"_84":9672,"_86":641,"_88":89},[8795,8806,8817,8839,8868,8919,8955,9012,9091,9128,9182,9219,9256,9293,9450,9473],{"_31":8796,"_33":8797},[],{"_35":160,"_37":8798,"_39":641,"_41":8799,"_66":8800,"_68":8805,"_70":69},"HNVkV_Rj",{},[8801],{"_35":166,"_167":8802,"_169":8803,"_41":8804,"_70":69},[137],[1488],{},"Satoshi Nakamoto",{"_31":8807,"_33":8808},[],{"_35":160,"_37":8809,"_39":641,"_41":8810,"_66":8811,"_68":8816,"_70":69},"iaE0Nhmv",{},[8812],{"_35":166,"_167":8813,"_169":8814,"_41":8815,"_70":69},[137],[1488],{},"October 31, 2008",{"_31":8818,"_33":8826},[8819],{"_31":8820,"_33":8821},[],{"_35":160,"_37":8822,"_39":641,"_41":8823,"_66":8824,"_68":8825,"_70":69},"kCo8J7Pg",{},[],"A purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution. Digital signatures provide part of the solution, but the main benefits are lost if a trusted third party is still required to prevent double-spending. We propose a solution to the double-spending problem using a peer-to-peer network. The network timestamps transactions by hashing them into an ongoing chain of hash-based proof-of-work, forming a record that cannot be changed without redoing the proof-of-work. The longest chain not only serves as proof of the sequence of events witnessed, but proof that it came from the largest pool of CPU power. As long as a majority of CPU power is controlled by nodes that are not cooperating to attack the network, they'll generate the longest chain and outpace attackers. The network itself requires minimal structure. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will, accepting the longest proof-of-work chain as proof of what happened while they were gone.",{"_35":870,"_37":8827,"_39":641,"_41":8828,"_66":8829,"_68":1827,"_70":69},"pQ0OBPyz",{},[8830,8834],{"_35":166,"_167":8831,"_169":8832,"_41":8833,"_70":69},[137],[240],{},{"_35":204,"_167":8835,"_169":8836,"_41":8837,"_70":8838},[137],[240],{},"https://nakamotoinstitute.org/bitcoin/#abstract",{"_31":8840,"_33":8855},[8841,8848],{"_31":8842,"_33":8843},[],{"_35":160,"_37":8844,"_39":641,"_41":8845,"_66":8846,"_68":8847,"_70":69},"jWY-Y6D6",{},[],"Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electronic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model. Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increases transaction costs, limiting the minimum practical transaction size and cutting off the possibility for small casual transactions, and there is a broader cost in the loss of ability to make non-reversible payments for non-reversible services. With the possibility of reversal, the need for trust spreads. Merchants must be wary of their customers, hassling them for more information than they would otherwise need. A certain percentage of fraud is accepted as unavoidable. These costs and payment uncertainties can be avoided in person by using physical currency, but no mechanism exists to make payments over a communications channel without a trusted party.",{"_31":8849,"_33":8850},[],{"_35":160,"_37":8851,"_39":641,"_41":8852,"_66":8853,"_68":8854,"_70":69},"PHk1QkGN",{},[],"What is needed is an electronic payment system based on cryptographic proof instead of trust, allowing any two willing parties to transact directly with each other without the need for a trusted third party. Transactions that are computationally impractical to reverse would protect sellers from fraud, and routine escrow mechanisms could easily be implemented to protect buyers. In this paper, we propose a solution to the double-spending problem using a peer-to-peer distributed timestamp server to generate computational proof of the chronological order of transactions. The system is secure as long as honest nodes collectively control more CPU power than any cooperating group of attacker nodes.",{"_35":870,"_37":8856,"_39":641,"_41":8857,"_66":8858,"_68":3644,"_70":69},"9sGRIlRH",{},[8859,8863],{"_35":166,"_167":8860,"_169":8861,"_41":8862,"_70":69},[137],[2828],{},{"_35":204,"_167":8864,"_169":8865,"_41":8866,"_70":8867},[137],[2828],{},"https://nakamotoinstitute.org/bitcoin/#introduction",{"_31":8869,"_33":8905},[8870,8877,8884,8891],{"_31":8871,"_33":8872},[],{"_35":160,"_37":8873,"_39":641,"_41":8874,"_66":8875,"_68":8876,"_70":69},"R5WfY63y",{},[],"We define an electronic coin as a chain of digital signatures. Each owner transfers the coin to the next by digitally signing a hash of the previous transaction and the public key of the next owner and adding these to the end of the coin. A payee can verify the signatures to verify the chain of ownership.",{"_31":8878,"_33":8879},[],{"_35":1875,"_37":8880,"_39":641,"_41":8881,"_66":8882,"_68":69,"_70":8883},"MeBqGm1Q",{"_273":323},[],"ipfs://bafkreib4meyv5hau4dwqs7by22dezuv6bwkuostrcny67q6e2vgfxyyex4",{"_31":8885,"_33":8886},[],{"_35":160,"_37":8887,"_39":641,"_41":8888,"_66":8889,"_68":8890,"_70":69},"qsJVvV7s",{},[],"The problem of course is the payee can't verify that one of the owners did not double-spend the coin. A common solution is to introduce a trusted central authority, or mint, that checks every transaction for double spending. After each transaction, the coin must be returned to the mint to issue a new coin, and only coins issued directly from the mint are trusted not to be double-spent. The problem with this solution is that the fate of the entire money system depends on the company running the mint, with every transaction having to go through them, just like a bank.",{"_31":8892,"_33":8893},[],{"_35":160,"_37":8894,"_39":641,"_41":8895,"_66":8896,"_68":8904,"_70":69},"iOhTN5L1",{},[8897],{"_35":204,"_167":8898,"_169":8900,"_41":8902,"_70":8903},[8899],491,[8901],494,{},"https://nakamotoinstitute.org/bitcoin/#fn1","We need a way for the payee to know that the previous owners did not sign any earlier transactions. For our purposes, the earliest transaction is the one that counts, so we don't care about later attempts to double-spend. The only way to confirm the absence of a transaction is to be aware of all transactions. In the mint based model, the mint was aware of all transactions and decided which arrived first. To accomplish this without a trusted party, transactions must be publicly announced[1], and we need a system for participants to agree on a single history of the order in which they were received. The payee needs proof that at the time of each transaction, the majority of nodes agreed it was the first received.",{"_35":870,"_37":8906,"_39":641,"_41":8907,"_66":8908,"_68":8918,"_70":69},"J7Dg1bVM",{},[8909,8913],{"_35":166,"_167":8910,"_169":8911,"_41":8912,"_70":69},[137],[2828],{},{"_35":204,"_167":8914,"_169":8915,"_41":8916,"_70":8917},[137],[2828],{},"https://nakamotoinstitute.org/bitcoin/#transactions","2. Transactions",{"_31":8920,"_33":8941},[8921,8934],{"_31":8922,"_33":8923},[],{"_35":160,"_37":8924,"_39":641,"_41":8925,"_66":8926,"_68":8933,"_70":69},"WQO8i5l7",{},[8927],{"_35":204,"_167":8928,"_169":8930,"_41":8931,"_70":8932},[8929],205,[7213],{},"https://nakamotoinstitute.org/bitcoin/#fn2","The solution we propose begins with a timestamp server. A timestamp server works by taking a hash of a block of items to be timestamped and widely publishing the hash, such as in a newspaper or Usenet post[2-5]. The timestamp proves that the data must have existed at the time, obviously, in order to get into the hash. Each timestamp includes the previous timestamp in its hash, forming a chain, with each additional timestamp reinforcing the ones before it.",{"_31":8935,"_33":8936},[],{"_35":1875,"_37":8937,"_39":641,"_41":8938,"_66":8939,"_68":69,"_70":8940},"UnYaJtxx",{"_273":323},[],"ipfs://bafkreic6cq4efid3zaurju5arjgt5lztptsf27x53aqsoipcg6irhuvom4",{"_35":870,"_37":8942,"_39":641,"_41":8943,"_66":8944,"_68":8954,"_70":69},"yMrTBh1k",{},[8945,8949],{"_35":166,"_167":8946,"_169":8947,"_41":8948,"_70":69},[137],[985],{},{"_35":204,"_167":8950,"_169":8951,"_41":8952,"_70":8953},[137],[985],{},"https://nakamotoinstitute.org/bitcoin/#timestamp-server","3. Timestamp Server",{"_31":8956,"_33":8998},[8957,8970,8977,8984,8991],{"_31":8958,"_33":8959},[],{"_35":160,"_37":8960,"_39":641,"_41":8961,"_66":8962,"_68":8969,"_70":69},"ayevYwmO",{},[8963],{"_35":204,"_167":8964,"_169":8965,"_41":8967,"_70":8968},[6411],[8966],146,{},"https://nakamotoinstitute.org/bitcoin/#fn6","To implement a distributed timestamp server on a peer-to-peer basis, we will need to use a proof-of-work system similar to Adam Back's Hashcash[6], rather than newspaper or Usenet posts. The proof-of-work involves scanning for a value that when hashed, such as with SHA-256, the hash begins with a number of zero bits. The average work required is exponential in the number of zero bits required and can be verified by executing a single hash.",{"_31":8971,"_33":8972},[],{"_35":160,"_37":8973,"_39":641,"_41":8974,"_66":8975,"_68":8976,"_70":69},"sRwP_Uc5",{},[],"For our timestamp network, we implement the proof-of-work by incrementing a nonce in the block until a value is found that gives the block's hash the required zero bits. Once the CPU effort has been expended to make it satisfy the proof-of-work, the block cannot be changed without redoing the work. As later blocks are chained after it, the work to change the block would include redoing all the blocks after it.",{"_31":8978,"_33":8979},[],{"_35":1875,"_37":8980,"_39":641,"_41":8981,"_66":8982,"_68":69,"_70":8983},"OtvgfOVN",{"_273":323},[],"ipfs://bafkreiahzzkrdps5wi74hqffkz2fvebt4mvvgyavdhnogbudub4hfgxtpm",{"_31":8985,"_33":8986},[],{"_35":160,"_37":8987,"_39":641,"_41":8988,"_66":8989,"_68":8990,"_70":69},"GW_zkZNu",{},[],"The proof-of-work also solves the problem of determining representation in majority decision making. If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs. Proof-of-work is essentially one-CPU-one-vote. The majority decision is represented by the longest chain, which has the greatest proof-of-work effort invested in it. If a majority of CPU power is controlled by honest nodes, the honest chain will grow the fastest and outpace any competing chains. To modify a past block, an attacker would have to redo the proof-of-work of the block and all blocks after it and then catch up with and surpass the work of the honest nodes. We will show later that the probability of a slower attacker catching up diminishes exponentially as subsequent blocks are added.",{"_31":8992,"_33":8993},[],{"_35":160,"_37":8994,"_39":641,"_41":8995,"_66":8996,"_68":8997,"_70":69},"YUtnyzrd",{},[],"To compensate for increasing hardware speed and varying interest in running nodes over time, the proof-of-work difficulty is determined by a moving average targeting an average number of blocks per hour. If they're generated too fast, the difficulty increases.",{"_35":870,"_37":8999,"_39":641,"_41":9000,"_66":9001,"_68":9011,"_70":69},"nf2b7GGB",{},[9002,9006],{"_35":166,"_167":9003,"_169":9004,"_41":9005,"_70":69},[137],[1488],{},{"_35":204,"_167":9007,"_169":9008,"_41":9009,"_70":9010},[137],[1488],{},"https://nakamotoinstitute.org/bitcoin/#proof-of-work","4. Proof-of-Work",{"_31":9013,"_33":9077},[9014,9063,9070],{"_31":9015,"_33":9058},[9016,9023,9030,9037,9044,9051],{"_31":9017,"_33":9018},[],{"_35":160,"_37":9019,"_39":641,"_41":9020,"_66":9021,"_68":9022,"_70":69},"xnZyeCk2",{},[],"New transactions are broadcast to all nodes.",{"_31":9024,"_33":9025},[],{"_35":160,"_37":9026,"_39":641,"_41":9027,"_66":9028,"_68":9029,"_70":69},"AlsfKdCK",{},[],"Each node collects new transactions into a block.",{"_31":9031,"_33":9032},[],{"_35":160,"_37":9033,"_39":641,"_41":9034,"_66":9035,"_68":9036,"_70":69},"y7SelTcb",{},[],"Each node works on finding a difficult proof-of-work for its block.",{"_31":9038,"_33":9039},[],{"_35":160,"_37":9040,"_39":641,"_41":9041,"_66":9042,"_68":9043,"_70":69},"NwjkTm5j",{},[],"When a node finds a proof-of-work, it broadcasts the block to all nodes.",{"_31":9045,"_33":9046},[],{"_35":160,"_37":9047,"_39":641,"_41":9048,"_66":9049,"_68":9050,"_70":69},"POHtdPnm",{},[],"Nodes accept the block only if all transactions in it are valid and not already spent.",{"_31":9052,"_33":9053},[],{"_35":160,"_37":9054,"_39":641,"_41":9055,"_66":9056,"_68":9057,"_70":69},"QX5Js2Lg",{},[],"Nodes express their acceptance of the block by working on creating the next block in the chain, using the hash of the accepted block as the previous hash.",{"_35":160,"_37":9059,"_39":641,"_41":9060,"_66":9061,"_68":9062,"_70":69},"stjxMQ1o",{"_273":2113},[],"The steps to run the network are as follows:",{"_31":9064,"_33":9065},[],{"_35":160,"_37":9066,"_39":641,"_41":9067,"_66":9068,"_68":9069,"_70":69},"9XCQHXzN",{},[],"Nodes always consider the longest chain to be the correct one and will keep working on extending it. If two nodes broadcast different versions of the next block simultaneously, some nodes may receive one or the other first. In that case, they work on the first one they received, but save the other branch in case it becomes longer. The tie will be broken when the next proof-of-work is found and one branch becomes longer; the nodes that were working on the other branch will then switch to the longer one.",{"_31":9071,"_33":9072},[],{"_35":160,"_37":9073,"_39":641,"_41":9074,"_66":9075,"_68":9076,"_70":69},"9BXGFX94",{},[],"New transaction broadcasts do not necessarily need to reach all nodes. As long as they reach many nodes, they will get into a block before long. Block broadcasts are also tolerant of dropped messages. If a node does not receive a block, it will request it when it receives the next block and realizes it missed one.",{"_35":870,"_37":9078,"_39":641,"_41":9079,"_66":9080,"_68":9090,"_70":69},"4X-jcZsW",{},[9081,9085],{"_35":166,"_167":9082,"_169":9083,"_41":9084,"_70":69},[137],[6982],{},{"_35":204,"_167":9086,"_169":9087,"_41":9088,"_70":9089},[137],[6982],{},"https://nakamotoinstitute.org/bitcoin/#network","5. Network",{"_31":9092,"_33":9114},[9093,9100,9107],{"_31":9094,"_33":9095},[],{"_35":160,"_37":9096,"_39":641,"_41":9097,"_66":9098,"_68":9099,"_70":69},"DcJNmWb1",{},[],"By convention, the first transaction in a block is a special transaction that starts a new coin owned by the creator of the block. This adds an incentive for nodes to support the network, and provides a way to initially distribute coins into circulation, since there is no central authority to issue them. The steady addition of a constant of amount of new coins is analogous to gold miners expending resources to add gold to circulation. In our case, it is CPU time and electricity that is expended.",{"_31":9101,"_33":9102},[],{"_35":160,"_37":9103,"_39":641,"_41":9104,"_66":9105,"_68":9106,"_70":69},"Ii3Gc6bh",{},[],"The incentive can also be funded with transaction fees. If the output value of a transaction is less than its input value, the difference is a transaction fee that is added to the incentive value of the block containing the transaction. Once a predetermined number of coins have entered circulation, the incentive can transition entirely to transaction fees and be completely inflation free.",{"_31":9108,"_33":9109},[],{"_35":160,"_37":9110,"_39":641,"_41":9111,"_66":9112,"_68":9113,"_70":69},"_aY-zK4q",{},[],"The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth.",{"_35":870,"_37":9115,"_39":641,"_41":9116,"_66":9117,"_68":9127,"_70":69},"jDpfMGhC",{},[9118,9122],{"_35":166,"_167":9119,"_169":9120,"_41":9121,"_70":69},[137],[1542],{},{"_35":204,"_167":9123,"_169":9124,"_41":9125,"_70":9126},[137],[1542],{},"https://nakamotoinstitute.org/bitcoin/#incentive","6. Incentive",{"_31":9129,"_33":9168},[9130,9154,9161],{"_31":9131,"_33":9132},[],{"_35":160,"_37":9133,"_39":641,"_41":9134,"_66":9135,"_68":9153,"_70":69},"lRg_J6DG",{},[9136,9142,9147],{"_35":204,"_167":9137,"_169":9138,"_41":9140,"_70":9141},[6375],[9139],237,{},"https://nakamotoinstitute.org/bitcoin/#fn7",{"_35":204,"_167":9143,"_169":9144,"_41":9146,"_70":8932},[9139],[9145],240,{},{"_35":204,"_167":9148,"_169":9149,"_41":9151,"_70":9152},[9145],[9150],243,{},"https://nakamotoinstitute.org/bitcoin/#fn5","Once the latest transaction in a coin is buried under enough blocks, the spent transactions before it can be discarded to save disk space. To facilitate this without breaking the block's hash, transactions are hashed in a Merkle Tree [7][2][5], with only the root included in the block's hash. Old blocks can then be compacted by stubbing off branches of the tree. The interior hashes do not need to be stored.",{"_31":9155,"_33":9156},[],{"_35":1875,"_37":9157,"_39":641,"_41":9158,"_66":9159,"_68":69,"_70":9160},"jaLqvM2d",{"_273":323},[],"ipfs://bafkreifwfibgbkxosbamhxh2yb7lzlolgjmtuqivxmbcseuuucxuydbmem",{"_31":9162,"_33":9163},[],{"_35":160,"_37":9164,"_39":641,"_41":9165,"_66":9166,"_68":9167,"_70":69},"TqnqJuzW",{},[],"A block header with no transactions would be about 80 bytes. If we suppose blocks are generated every 10 minutes, 80 bytes *6 *24 * 365 = 4.2MB per year. With computer systems typically selling with 2GB of RAM as of 2008, and Moore's Law predicting current growth of 1.2GB per year, storage should not be a problem even if the block headers must be kept in memory.",{"_35":870,"_37":9169,"_39":641,"_41":9170,"_66":9171,"_68":9181,"_70":69},"vGE1pRQD",{},[9172,9176],{"_35":166,"_167":9173,"_169":9174,"_41":9175,"_70":69},[137],[2531],{},{"_35":204,"_167":9177,"_169":9178,"_41":9179,"_70":9180},[137],[2531],{},"https://nakamotoinstitute.org/bitcoin/#reclaiming-disk-space","7. Reclaiming Disk Space",{"_31":9183,"_33":9205},[9184,9191,9198],{"_31":9185,"_33":9186},[],{"_35":160,"_37":9187,"_39":641,"_41":9188,"_66":9189,"_68":9190,"_70":69},"4yn7hfYh",{},[],"It is possible to verify payments without running a full network node. A user only needs to keep a copy of the block headers of the longest proof-of-work chain, which he can get by querying network nodes until he's convinced he has the longest chain, and obtain the Merkle branch linking the transaction to the block it's timestamped in. He can't check the transaction for himself, but by linking it to a place in the chain, he can see that a network node has accepted it, and blocks added after it further confirm the network has accepted it.",{"_31":9192,"_33":9193},[],{"_35":1875,"_37":9194,"_39":641,"_41":9195,"_66":9196,"_68":69,"_70":9197},"V8FGyatp",{"_273":323},[],"ipfs://bafkreihe3ah73hf2oc2ma3x6acjfxqbk3ot2tuqxoy4siriiql52g33b74",{"_31":9199,"_33":9200},[],{"_35":160,"_37":9201,"_39":641,"_41":9202,"_66":9203,"_68":9204,"_70":69},"wkNlj9f3",{},[],"As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker. While network nodes can verify transactions for themselves, the simplified method can be fooled by an attacker's fabricated transactions for as long as the attacker can continue to overpower the network. One strategy to protect against this would be to accept alerts from network nodes when they detect an invalid block, prompting the user's software to download the full block and alerted transactions to confirm the inconsistency. Businesses that receive frequent payments will probably still want to run their own nodes for more independent security and quicker verification.",{"_35":870,"_37":9206,"_39":641,"_41":9207,"_66":9208,"_68":9218,"_70":69},"eG3kSsAV",{},[9209,9213],{"_35":166,"_167":9210,"_169":9211,"_41":9212,"_70":69},[137],[2477],{},{"_35":204,"_167":9214,"_169":9215,"_41":9216,"_70":9217},[137],[2477],{},"https://nakamotoinstitute.org/bitcoin/#simplified-payment-verification","8. Simplified Payment Verification",{"_31":9220,"_33":9242},[9221,9228,9235],{"_31":9222,"_33":9223},[],{"_35":160,"_37":9224,"_39":641,"_41":9225,"_66":9226,"_68":9227,"_70":69},"2TUseBgq",{},[],"Although it would be possible to handle coins individually, it would be unwieldy to make a separate transaction for every cent in a transfer. To allow value to be split and combined, transactions contain multiple inputs and outputs. Normally there will be either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and at most two outputs: one for the payment, and one returning the change, if any, back to the sender.",{"_31":9229,"_33":9230},[],{"_35":1875,"_37":9231,"_39":641,"_41":9232,"_66":9233,"_68":69,"_70":9234},"cTfiGxY8",{"_273":323},[],"ipfs://bafkreiexkeqida4d2ozl4ctpdlhbfnwqbashq6zobmxmoiijqgubdj5pra",{"_31":9236,"_33":9237},[],{"_35":160,"_37":9238,"_39":641,"_41":9239,"_66":9240,"_68":9241,"_70":69},"2WER_WHe",{},[],"It should be noted that fan-out, where a transaction depends on several transactions, and those transactions depend on many more, is not a problem here. There is never the need to extract a complete standalone copy of a transaction's history.",{"_35":870,"_37":9243,"_39":641,"_41":9244,"_66":9245,"_68":9255,"_70":69},"d8T_XpXO",{},[9246,9250],{"_35":166,"_167":9247,"_169":9248,"_41":9249,"_70":69},[137],[987],{},{"_35":204,"_167":9251,"_169":9252,"_41":9253,"_70":9254},[137],[987],{},"https://nakamotoinstitute.org/bitcoin/#combining-and-splitting-value","9. Combining and Splitting Value",{"_31":9257,"_33":9279},[9258,9265,9272],{"_31":9259,"_33":9260},[],{"_35":160,"_37":9261,"_39":641,"_41":9262,"_66":9263,"_68":9264,"_70":69},"UQGJzaIy",{},[],"The traditional banking model achieves a level of privacy by limiting access to information to the parties involved and the trusted third party. The necessity to announce all transactions publicly precludes this method, but privacy can still be maintained by breaking the flow of information in another place: by keeping public keys anonymous. The public can see that someone is sending an amount to someone else, but without information linking the transaction to anyone. This is similar to the level of information released by stock exchanges, where the time and size of individual trades, the \"tape\", is made public, but without telling who the parties were.",{"_31":9266,"_33":9267},[],{"_35":1875,"_37":9268,"_39":641,"_41":9269,"_66":9270,"_68":69,"_70":9271},"p3YG9N3n",{"_273":323},[],"ipfs://bafkreidcqqcx3tp4uzjuxrvytcxgrurtu4k27xvxqy65skctg2kbmd65xm",{"_31":9273,"_33":9274},[],{"_35":160,"_37":9275,"_39":641,"_41":9276,"_66":9277,"_68":9278,"_70":69},"dnvQ2Xvy",{},[],"As an additional firewall, a new key pair should be used for each transaction to keep them from being linked to a common owner. Some linking is still unavoidable with multi-input transactions, which necessarily reveal that their inputs were owned by the same owner. The risk is that if the owner of a key is revealed, linking could reveal other transactions that belonged to the same owner.",{"_35":870,"_37":9280,"_39":641,"_41":9281,"_66":9282,"_68":9292,"_70":69},"L2MOTmjX",{},[9283,9287],{"_35":166,"_167":9284,"_169":9285,"_41":9286,"_70":69},[137],[1464],{},{"_35":204,"_167":9288,"_169":9289,"_41":9290,"_70":9291},[137],[1464],{},"https://nakamotoinstitute.org/bitcoin/#privacy","10. Privacy",{"_31":9294,"_33":9436},[9295,9302,9309,9323,9331,9338,9345,9352,9359,9366,9373,9380,9387,9394,9401,9408,9415,9422,9429],{"_31":9296,"_33":9297},[],{"_35":160,"_37":9298,"_39":641,"_41":9299,"_66":9300,"_68":9301,"_70":69},"K0NAnVo6",{},[],"We consider the scenario of an attacker trying to generate an alternate chain faster than the honest chain. Even if this is accomplished, it does not throw the system open to arbitrary changes, such as creating value out of thin air or taking money that never belonged to the attacker. Nodes are not going to accept an invalid transaction as payment, and honest nodes will never accept a block containing them. An attacker can only try to change one of his own transactions to take back money he recently spent.",{"_31":9303,"_33":9304},[],{"_35":160,"_37":9305,"_39":641,"_41":9306,"_66":9307,"_68":9308,"_70":69},"dYSnFZKV",{},[],"The race between the honest chain and an attacker chain can be characterized as a Binomial Random Walk. The success event is the honest chain being extended by one block, increasing its lead by +1, and the failure event is the attacker's chain being extended by one block, reducing the gap by -1.",{"_31":9310,"_33":9311},[],{"_35":160,"_37":9312,"_39":641,"_41":9313,"_66":9314,"_68":9322,"_70":69},"6fyEYWrz",{},[9315],{"_35":204,"_167":9316,"_169":9318,"_41":9320,"_70":9321},[9317],373,[9319],376,{},"https://nakamotoinstitute.org/bitcoin/#fn8","The probability of an attacker catching up from a given deficit is analogous to a Gambler's Ruin problem. Suppose a gambler with unlimited credit starts at a deficit and plays potentially an infinite number of trials to try to reach breakeven. We can calculate the probability he ever reaches breakeven, or that an attacker ever catches up with the honest chain, as follows[8]:",{"_31":9324,"_33":9325},[],{"_35":2026,"_37":9326,"_39":641,"_41":9327,"_66":9329,"_68":9330,"_70":69},"W-K9bDsX",{"_2029":9328},"plaintext",[],"p = probability an honest node finds the next block\nq = probability the attacker finds the next block\nqz = probability the attacker will ever catch up from z blocks behind\n qz = {1 if p ≤ q\n (q/p)^z if if p fp>q}\n",{"_31":9332,"_33":9333},[],{"_35":160,"_37":9334,"_39":641,"_41":9335,"_66":9336,"_68":9337,"_70":69},"MgleBFro",{},[],"Given our assumption that p > q, the probability drops exponentially as the number of blocks the attacker has to catch up with increases. With the odds against him, if he doesn't make a lucky lunge forward early on, his chances become vanishingly small as he falls further behind.",{"_31":9339,"_33":9340},[],{"_35":160,"_37":9341,"_39":641,"_41":9342,"_66":9343,"_68":9344,"_70":69},"GOUDhFlD",{},[],"We now consider how long the recipient of a new transaction needs to wait before being sufficiently certain the sender can't change the transaction. We assume the sender is an attacker who wants to make the recipient believe he paid him for a while, then switch it to pay back to himself after some time has passed. The receiver will be alerted when that happens, but the sender hopes it will be too late.",{"_31":9346,"_33":9347},[],{"_35":160,"_37":9348,"_39":641,"_41":9349,"_66":9350,"_68":9351,"_70":69},"5lNdn4yV",{},[],"The receiver generates a new key pair and gives the public key to the sender shortly before signing. This prevents the sender from preparing a chain of blocks ahead of time by working on it continuously until he is lucky enough to get far enough ahead, then executing the transaction at that moment. Once the transaction is sent, the dishonest sender starts working in secret on a parallel chain containing an alternate version of his transaction.",{"_31":9353,"_33":9354},[],{"_35":160,"_37":9355,"_39":641,"_41":9356,"_66":9357,"_68":9358,"_70":69},"HjBIx8m3",{},[],"The recipient waits until the transaction has been added to a block and z� blocks have been linked after it. He doesn't know the exact amount of progress the attacker has made, but assuming the honest blocks took the average expected time per block, the attacker's potential progress will be a Poisson distribution with expected value:",{"_31":9360,"_33":9361},[],{"_35":1875,"_37":9362,"_39":641,"_41":9363,"_66":9364,"_68":69,"_70":9365},"6Y9YYQ3j",{"_273":323},[],"ipfs://bafkreidc2z5tfsj6b3z4ie5hljgbv2fhodifacbwayyi6qrfwq46aq6y5u",{"_31":9367,"_33":9368},[],{"_35":160,"_37":9369,"_39":641,"_41":9370,"_66":9371,"_68":9372,"_70":69},"sKyhgCA-",{},[],"To get the probability the attacker could still catch up now, we multiply the Poisson density for each amount of progress he could have made by the probability he could catch up from that point:",{"_31":9374,"_33":9375},[],{"_35":1875,"_37":9376,"_39":641,"_41":9377,"_66":9378,"_68":69,"_70":9379},"gw3a02Zs",{"_273":323},[],"ipfs://bafkreifmzf6lfegbwoe7dtdy2b52ges3octux543ggbu6qyrpkjyl5sqj4",{"_31":9381,"_33":9382},[],{"_35":160,"_37":9383,"_39":641,"_41":9384,"_66":9385,"_68":9386,"_70":69},"yabAdWnP",{},[],"Rearranging to avoid summing the infinite tail of the distribution...",{"_31":9388,"_33":9389},[],{"_35":1875,"_37":9390,"_39":641,"_41":9391,"_66":9392,"_68":69,"_70":9393},"r6mx3FhB",{"_273":323},[],"ipfs://bafkreifakkpyxatczdelxg7h3qb64ztcjambwtpecld74f6p6wvuwuyrnm",{"_31":9395,"_33":9396},[],{"_35":160,"_37":9397,"_39":641,"_41":9398,"_66":9399,"_68":9400,"_70":69},"tezfF5Bj",{},[],"Converting to C code...",{"_31":9402,"_33":9403},[],{"_35":2026,"_37":9404,"_39":641,"_41":9405,"_66":9406,"_68":9407,"_70":69},"q9JZj430",{"_2029":9328},[],"#include \ndouble AttackerSuccessProbability(double q, int z)\n{\n double p = 1.0 - q;\n double lambda = z * (q / p);\n double sum = 1.0;\n int i, k;\n for (k = 0; k <= z; k++)\n {\n double poisson = exp(-lambda);\n for (i = 1; i <= k; i++)\n poisson *= lambda / i;\n sum -= poisson * (1 - pow(q / p, z - k));\n }\n return sum;\n}\n",{"_31":9409,"_33":9410},[],{"_35":160,"_37":9411,"_39":641,"_41":9412,"_66":9413,"_68":9414,"_70":69},"kVweAf7z",{},[],"Running some results, we can see the probability drop off exponentially with z.",{"_31":9416,"_33":9417},[],{"_35":2026,"_37":9418,"_39":641,"_41":9419,"_66":9420,"_68":9421,"_70":69},"QlZ4SI99",{"_2029":9328},[],"q=0.1\nz=0 P=1.0000000\nz=1 P=0.2045873\nz=2 P=0.0509779\nz=3 P=0.0131722\nz=4 P=0.0034552\nz=5 P=0.0009137\nz=6 P=0.0002428\nz=7 P=0.0000647\nz=8 P=0.0000173\nz=9 P=0.0000046\nz=10 P=0.0000012\n\nq=0.3\nz=0 P=1.0000000\nz=5 P=0.1773523\nz=10 P=0.0416605\nz=15 P=0.0101008\nz=20 P=0.0024804\nz=25 P=0.0006132\nz=30 P=0.0001522\nz=35 P=0.0000379\nz=40 P=0.0000095\nz=45 P=0.0000024\nz=50 P=0.0000006\n",{"_31":9423,"_33":9424},[],{"_35":160,"_37":9425,"_39":641,"_41":9426,"_66":9427,"_68":9428,"_70":69},"BLv67_h8",{},[],"Solving for P less than 0.1%...",{"_31":9430,"_33":9431},[],{"_35":2026,"_37":9432,"_39":641,"_41":9433,"_66":9434,"_68":9435,"_70":69},"84XKlfIk",{"_2029":9328},[],"P < 0.001\nq=0.10 z=5\nq=0.15 z=8\nq=0.20 z=11\nq=0.25 z=15\nq=0.30 z=24\nq=0.35 z=41\nq=0.40 z=89\nq=0.45 z=340\n",{"_35":870,"_37":9437,"_39":641,"_41":9438,"_66":9439,"_68":9449,"_70":69},"nor-rS0A",{},[9440,9444],{"_35":166,"_167":9441,"_169":9442,"_41":9443,"_70":69},[137],[1488],{},{"_35":204,"_167":9445,"_169":9446,"_41":9447,"_70":9448},[137],[1488],{},"https://nakamotoinstitute.org/bitcoin/#calculations","11. Calculations",{"_31":9451,"_33":9459},[9452],{"_31":9453,"_33":9454},[],{"_35":160,"_37":9455,"_39":641,"_41":9456,"_66":9457,"_68":9458,"_70":69},"oge-XSqA",{},[],"We have proposed a system for electronic transactions without relying on trust. We started with the usual framework of coins made from digital signatures, which provides strong control of ownership, but is incomplete without a way to prevent double-spending. To solve this, we proposed a peer-to-peer network using proof-of-work to record a public history of transactions that quickly becomes computationally impractical for an attacker to change if honest nodes control a majority of CPU power. The network is robust in its unstructured simplicity. Nodes work all at once with little coordination. They do not need to be identified, since messages are not routed to any particular place and only need to be delivered on a best effort basis. Nodes can leave and rejoin the network at will, accepting the proof-of-work chain as proof of what happened while they were gone. They vote with their CPU power, expressing their acceptance of valid blocks by working on extending them and rejecting invalid blocks by refusing to work on them. Any needed rules and incentives can be enforced with this consensus mechanism.",{"_35":870,"_37":9460,"_39":641,"_41":9461,"_66":9462,"_68":9472,"_70":69},"_J_ObKpN",{},[9463,9467],{"_35":166,"_167":9464,"_169":9465,"_41":9466,"_70":69},[137],[171],{},{"_35":204,"_167":9468,"_169":9469,"_41":9470,"_70":9471},[137],[171],{},"https://nakamotoinstitute.org/bitcoin/#conclusion","12. Conclusion",{"_31":9474,"_33":9656},[9475,9498,9527,9549,9570,9596,9618,9639],{"_31":9476,"_33":9477},[],{"_35":160,"_37":9478,"_39":641,"_41":9479,"_66":9480,"_68":9497,"_70":69},"lBZatHCY",{},[9481,9486,9492],{"_35":204,"_167":9482,"_169":9483,"_41":9484,"_70":9485},[240],[6448],{},"https://nakamotoinstitute.org/b-money/",{"_35":204,"_167":9487,"_169":9488,"_41":9490,"_70":9491},[985],[9489],51,{},"http://www.weidai.com/bmoney.txt",{"_35":204,"_167":9493,"_169":9494,"_41":9495,"_70":9496},[1539],[6475],{},"https://nakamotoinstitute.org/bitcoin/#ref1","W. Dai, \"b-money,\" http://www.weidai.com/bmoney.txt, 1998. ↩",{"_31":9499,"_33":9500},[],{"_35":160,"_37":9501,"_39":641,"_41":9502,"_66":9503,"_68":9526,"_70":69},"ehJOLaPt",{},[9504,9509,9514,9519],{"_35":204,"_167":9505,"_169":9506,"_41":9507,"_70":9508},[6192],[1094],{},"https://nakamotoinstitute.org/static/docs/secure-timestamping-service.pdf",{"_35":919,"_167":9510,"_169":9512,"_41":9513,"_70":69},[9511],124,[244],{},{"_35":204,"_167":9515,"_169":9516,"_41":9517,"_70":9518},[1700],[5827],{},"https://nakamotoinstitute.org/bitcoin/#ref2",{"_35":204,"_167":9520,"_169":9522,"_41":9524,"_70":9525},[9521],189,[9523],190,{},"https://nakamotoinstitute.org/bitcoin/#ref2-2","H. Massias, X.S. Avila, and J.-J. Quisquater, \"Design of a secure timestamping service with minimal trust requirements,\" In 20th Symposium on Information Theory in the Benelux, May 1999. ↩ ↩",{"_31":9528,"_33":9529},[],{"_35":160,"_37":9530,"_39":641,"_41":9531,"_66":9532,"_68":9548,"_70":69},"4g73qCpe",{},[9533,9538,9543],{"_35":204,"_167":9534,"_169":9535,"_41":9536,"_70":9537},[3363],[6532],{},"https://nakamotoinstitute.org/literature/time-stamp-digital-document/",{"_35":919,"_167":9539,"_169":9540,"_41":9542,"_70":69},[5576],[9541],90,{},{"_35":204,"_167":9544,"_169":9545,"_41":9547,"_70":9518},[3376],[9546],126,{},"S. Haber, W.S. Stornetta, \"How to time-stamp a digital document,\" In Journal of Cryptology, vol 3, no 2, pages 99-111, 1991. ↩",{"_31":9550,"_33":9551},[],{"_35":160,"_37":9552,"_39":641,"_41":9553,"_66":9554,"_68":9569,"_70":69},"rxmMMfrP",{},[9555,9560,9564],{"_35":204,"_167":9556,"_169":9557,"_41":9558,"_70":9559},[1013],[6463],{},"https://nakamotoinstitute.org/literature/improving-time-stamping/",{"_35":919,"_167":9561,"_169":9562,"_41":9563,"_70":69},[6404],[6517],{},{"_35":204,"_167":9565,"_169":9567,"_41":9568,"_70":9518},[9566],200,[7134],{},"D. Bayer, S. Haber, W.S. Stornetta, \"Improving the efficiency and reliability of digital time-stamping,\" In Sequences II: Methods in Communication, Security and Computer Science, pages 329-334, 1993. ↩",{"_31":9571,"_33":9572},[],{"_35":160,"_37":9573,"_39":641,"_41":9574,"_66":9575,"_68":9595,"_70":69},"Lk4cXFCp",{},[9576,9581,9585,9590],{"_35":204,"_167":9577,"_169":9578,"_41":9579,"_70":9580},[3363],[263],{},"https://nakamotoinstitute.org/static/docs/secure-names-bit-strings.pdf",{"_35":919,"_167":9582,"_169":9583,"_41":9584,"_70":69},[265],[1248],{},{"_35":204,"_167":9586,"_169":9587,"_41":9589,"_70":9518},[973],[9588],166,{},{"_35":204,"_167":9591,"_169":9592,"_41":9593,"_70":9594},[2068],[3527],{},"https://nakamotoinstitute.org/bitcoin/#ref5","S. Haber, W.S. Stornetta, \"Secure names for bit-strings,\" In Proceedings of the 4th ACM Conference on Computer and Communications Security, pages 28-35, April 1997. ↩ ↩",{"_31":9597,"_33":9598},[],{"_35":160,"_37":9599,"_39":641,"_41":9600,"_66":9601,"_68":9617,"_70":69},"lvrgnju9",{},[9602,9607,9612],{"_35":204,"_167":9603,"_169":9604,"_41":9605,"_70":9606},[1476],[3453],{},"https://nakamotoinstitute.org/static/docs/hashcash.pdf",{"_35":204,"_167":9608,"_169":9609,"_41":9610,"_70":9611},[1539],[7328],{},"http://www.hashcash.org/papers/hashcash.pdf",{"_35":204,"_167":9613,"_169":9614,"_41":9615,"_70":9616},[6278],[5845],{},"https://nakamotoinstitute.org/bitcoin/#ref6","A. Back, \"Hashcash - a denial of service counter-measure,\" http://www.hashcash.org/papers/hashcash.pdf, 2002. ↩",{"_31":9619,"_33":9620},[],{"_35":160,"_37":9621,"_39":641,"_41":9622,"_66":9623,"_68":9638,"_70":69},"CpqEvRWV",{},[9624,9629,9633],{"_35":204,"_167":9625,"_169":9626,"_41":9627,"_70":9628},[1520],[6334],{},"https://nakamotoinstitute.org/literature/public-key-cryptosystems/",{"_35":919,"_167":9630,"_169":9631,"_41":9632,"_70":69},[3453],[7328],{},{"_35":204,"_167":9634,"_169":9635,"_41":9636,"_70":9637},[6476],[5974],{},"https://nakamotoinstitute.org/bitcoin/#ref7","R.C. Merkle, \"Protocols for public key cryptosystems,\" In Proc. 1980 Symposium on Security and Privacy, IEEE Computer Society, pages 122-133, April 1980. ↩",{"_31":9640,"_33":9641},[],{"_35":160,"_37":9642,"_39":641,"_41":9643,"_66":9644,"_68":9655,"_70":69},"sH7mLQBm",{},[9645,9650],{"_35":204,"_167":9646,"_169":9647,"_41":9648,"_70":9649},[1464],[1707],{},"https://nakamotoinstitute.org/literature/introduction-probability-theory-vol-i/",{"_35":204,"_167":9651,"_169":9652,"_41":9653,"_70":9654},[6450],[1117],{},"https://nakamotoinstitute.org/bitcoin/#ref8","W. Feller, \"An introduction to probability theory and its applications,\" 1957. ↩",{"_35":870,"_37":9657,"_39":641,"_41":9658,"_66":9659,"_68":3495,"_70":69},"NUco6M45",{"_273":2113},[9660,9664],{"_35":166,"_167":9661,"_169":9662,"_41":9663,"_70":69},[137],[6982],{},{"_35":204,"_167":9665,"_169":9666,"_41":9667,"_70":9668},[137],[6982],{},"https://nakamotoinstitute.org/bitcoin/#references",[644],"/records/bitcoin-a-peer-to-peer-electronic-cash-system",{"_82":657},{},{"_37":638,"_95":53,"_54":9674,"_71":641,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,640],1772031973218,[149,638,641],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/bitcoin-a-peer-to-peer-electronic-cash-system\",\"bafy2bzacec5sacme4htf7rr2af4s73pq32kq6s6gdq335d3dqumpt5rentpjc\"]",{"_110":9679,"_147":10454,"_150":10455},{"_112":9680,"_131":132,"_133":10453,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":9681,"_37":10451},{"_28":9682,"_71":663,"_72":53,"_73":10447,"_54":10448,"_76":670,"_78":670,"_80":10449,"_84":10450,"_86":663,"_88":89},[9683,9690,9696,9703,9710,9717,9724,9731,9738,9745,9752,9759,9766,9776,9783,9790,9797,9811,9825,9839,9846,9853,9860,9866,9873,9880,9887,9894,9943,10048,10195,10223,10230,10237,10244,10251,10258,10293,10300,10307,10314,10321,10328,10384,10391],{"_31":9684,"_33":9685},[],{"_35":160,"_37":9686,"_39":663,"_41":9687,"_66":9688,"_68":9689,"_70":69},"QQnpcIHS",{},[],"Theodor H. Nelson\nThis paper was presented at the International Conference on online interactive computing held at Brunei University, Uxbridge, England, September 4-7,1972.",{"_31":9691,"_33":9692},[],{"_35":870,"_37":9693,"_39":663,"_41":9694,"_66":9695,"_68":1827,"_70":69},"XQLzQI6D",{},[],{"_31":9697,"_33":9698},[],{"_35":160,"_37":9699,"_39":663,"_41":9700,"_66":9701,"_68":9702,"_70":69},"gNCUISFe",{},[],"Bush was right. His famous article is, however, generally misinterpreted, for it has little to do with \"information retrieval\" as prosecuted today. Bush rejected indexing and discussed instead new forms of interwoven documents.",{"_31":9704,"_33":9705},[],{"_35":160,"_37":9706,"_39":663,"_41":9707,"_66":9708,"_68":9709,"_70":69},"N2CzMsHM",{},[],"It is possible that Bush's vision will be fulfilled substantially as he saw it, and that information retrieval systems of the kinds now popular will see less use than anticipated.",{"_31":9711,"_33":9712},[],{"_35":160,"_37":9713,"_39":663,"_41":9714,"_66":9715,"_68":9716,"_70":69},"G2mKHD0A",{},[],"As the technological base has changed, we must recast his thesis slightly, and regard Bush's \"memex\" as three things: the personal presentation, editing and file console; a digital feeder network for the delivery of documents in full-text digital form; and new types of documents, or hypertexts, which are especially worth receiving and sending in this manner.",{"_31":9718,"_33":9719},[],{"_35":160,"_37":9720,"_39":663,"_41":9721,"_66":9722,"_68":9723,"_70":69},"ZV011Qi9",{},[],"In addition, we also consider a likely design for specialist hypertexts, and discuss problems of their publication.",{"_31":9725,"_33":9726},[],{"_35":870,"_37":9727,"_39":663,"_41":9728,"_66":9729,"_68":9730,"_70":69},"txHq26eE",{},[],"Beating Around the Bush",{"_31":9732,"_33":9733},[],{"_35":160,"_37":9734,"_39":663,"_41":9735,"_66":9736,"_68":9737,"_70":69},"KRDSg6M6",{},[],"Twenty-seven years ago, in a widely acclaimed article, Vannevar Bush made certain predictions about the way we of the future would handle written information (1). We are not yet doing so. Yet the Bush article is often cited as the historical beginning, or as a technological watershed, of the field of information retrieval. It is frequently cited without interpretation (2,3). Although some commentators have said its predictions were improbable (4), in general its precepts have been ignored by acclamation.",{"_31":9739,"_33":9740},[],{"_35":160,"_37":9741,"_39":663,"_41":9742,"_66":9743,"_68":9744,"_70":69},"HXVjZdSV",{},[],"In this paper, an effort in counter-discipleship, I hope to remind readers of what Bush did and did not say, and point out what is not yet recognized: that much of what he predicted is possible now; the memex is here; the \"trails\" he spoke of—suitably generalized, and now called hypertexts—may, and should, become the principal publishing form of the future.",{"_31":9746,"_33":9747},[],{"_35":160,"_37":9748,"_39":663,"_41":9749,"_66":9750,"_68":9751,"_70":69},"eVkhIxCG",{},[],"In July of 1945 an article entitled \"As We May Think,\" by Vannevar Bush, was published in the Atlantic Monthly. It bristled with technical references but was actually fairly candid and simple.",{"_31":9753,"_33":9754},[],{"_35":160,"_37":9755,"_39":663,"_41":9756,"_66":9757,"_68":9758,"_70":69},"LBWp1Zqo",{},[],"It predicted many things. Bush, as director of Roosevelt's wartime Office of Scientific Research and Development, had seen the new ways in which technologies could be combined. In the urbane paragraphs of this article, Bush predicted a variety of useful future machines, including improvements in photography, facsimile systems, computers and miscellany. Depending on how you read it, he predicted, as well as you could hope, devices closely related to the Polaroid camera, the Xerox machine, computer transformation of mathematical expressions, and the telephone company's ESS switching system.",{"_31":9760,"_33":9761},[],{"_35":160,"_37":9762,"_39":663,"_41":9763,"_66":9764,"_68":9765,"_70":69},"dbHrGh9m",{},[],"But the article is best remembered for its description of the new ways that scientists and scholars could handle and share their ideas, writing, reading and filing in a magical system at their desks. The system is the famous \"memex.\"",{"_31":9767,"_33":9768},[],{"_35":9769,"_37":9770,"_39":663,"_41":9771,"_66":9774,"_68":69,"_70":9775},"Embed","Osvz_xGC",{"_9772":9773},"view","Content",[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#AqGRgRAh",{"_31":9777,"_33":9778},[],{"_35":9769,"_37":9779,"_39":663,"_41":9780,"_66":9781,"_68":69,"_70":9782},"iTALYgzT",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#TfWCAxXp",{"_31":9784,"_33":9785},[],{"_35":160,"_37":9786,"_39":663,"_41":9787,"_66":9788,"_68":9789,"_70":69},"Y5L1E35K",{},[],"The memex will hold all the writings its master wants to read, and he can read them easily.",{"_31":9791,"_33":9792},[],{"_35":9769,"_37":9793,"_39":663,"_41":9794,"_66":9795,"_68":69,"_70":9796},"EfyNN9um",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#3lraYLjj",{"_31":9798,"_33":9806},[9799],{"_31":9800,"_33":9801},[],{"_35":9769,"_37":9802,"_39":663,"_41":9803,"_66":9804,"_68":69,"_70":9805},"Zy29M0BN",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#EN57UWfJ",{"_35":160,"_37":9807,"_39":663,"_41":9808,"_66":9809,"_68":9810,"_70":69},"hn9y-2-Y",{"_273":323},[],"Moreover, he can compare and annotate them.",{"_31":9812,"_33":9820},[9813],{"_31":9814,"_33":9815},[],{"_35":9769,"_37":9816,"_39":663,"_41":9817,"_66":9818,"_68":69,"_70":9819},"SJDERbDF",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#TlXiaXp1",{"_35":160,"_37":9821,"_39":663,"_41":9822,"_66":9823,"_68":9824,"_70":69},"u-YHRstV",{"_273":323},[],"Not only ordinary documents need be held in the memex. The user may make connections between different parts of the things stored. He does this by ",{"_31":9826,"_33":9834},[9827],{"_31":9828,"_33":9829},[],{"_35":9769,"_37":9830,"_39":663,"_41":9831,"_66":9832,"_68":69,"_70":9833},"V0bfhFCG",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#aJ5f5jF5",{"_35":160,"_37":9835,"_39":663,"_41":9836,"_66":9837,"_68":9838,"_70":69},"UN8-5owL",{"_273":323},[],"By this associative technique he may create \"trails,\" new documentary objects that are useful in new ways.",{"_31":9840,"_33":9841},[],{"_35":160,"_37":9842,"_39":663,"_41":9843,"_66":9844,"_68":9845,"_70":69},"0qS5JIc9",{},[],"These new structures, or trails, may be taken and given to other people.",{"_31":9847,"_33":9848},[],{"_35":9769,"_37":9849,"_39":663,"_41":9850,"_66":9851,"_68":69,"_70":9852},"Qh5Esiow",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#DAwmGiOq",{"_31":9854,"_33":9855},[],{"_35":160,"_37":9856,"_39":663,"_41":9857,"_66":9858,"_68":9859,"_70":69},"IySC15lW",{},[],"And they may be published.",{"_31":9861,"_33":9862},[],{"_35":9769,"_37":9863,"_39":663,"_41":9864,"_66":9865,"_68":69,"_70":9833},"AYnznU_y",{"_9772":9773},[],{"_31":9867,"_33":9868},[],{"_35":160,"_37":9869,"_39":663,"_41":9870,"_66":9871,"_68":9872,"_70":69},"frKQTh2a",{},[],"It is strange that \"As We May Think\" has been taken so to heart in the field of information retrieval, since it runs counter to virtually all work being pursued under the name of information retrieval today. Such systems are principally concerned either with indexing conventional documents by content, or with somehow representing that content in a way that can be mechanically searched and deciphered.",{"_31":9874,"_33":9875},[],{"_35":160,"_37":9876,"_39":663,"_41":9877,"_66":9878,"_68":9879,"_70":69},"2q1LvZDy",{},[],"This is indeed paradoxical. On the one hand, Bush did not think well of indexing.",{"_31":9881,"_33":9882},[],{"_35":9769,"_37":9883,"_39":663,"_41":9884,"_66":9885,"_68":69,"_70":9886},"aYi-2PDe",{"_9772":9773},[],"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/as-we-may-think?v=bafy2bzaceaqvup7xqozrjgf5aadd7ud7bey44u5zmekpj3w76qscejbnnc4gy#-UV4qKcD",{"_31":9888,"_33":9889},[],{"_35":160,"_37":9890,"_39":663,"_41":9891,"_66":9892,"_68":9893,"_70":69},"xv7hjJiW",{},[],"On the other hand, with regard to content retrieval. Bush merely hinted about the use of structured-data representations and calculi in storing ideas (105, col. 2, para. 3), and did not plainly relate them to his mail exposition. The reason is plain: his real emphasis was on linkage, an£ new structures and activities that the automatic link-jump would mak( possible. While we might argue scripture about such matters, the fact L that Bush's most extensive concern has had few successors in the fielf called \"information retrieval.\"",{"_31":9895,"_33":9938},[9896,9903,9910,9917,9924,9931],{"_31":9897,"_33":9898},[],{"_35":160,"_37":9899,"_39":663,"_41":9900,"_66":9901,"_68":9902,"_70":69},"QtWm_YHF",{},[],"The memex was to be a single screen console for handling the user's notes, writing and correspondence, for reading books and other writ¬ ings created by others, and for creating new associative text structures, which may in their turn be read and distributed. All this I take to be the heart of Bush's prediction. This will happen. Such systems exist; they are approaching cost feasibility; and the world is readier than it thinks.",{"_31":9904,"_33":9905},[],{"_35":160,"_37":9906,"_39":663,"_41":9907,"_66":9908,"_68":9909,"_70":69},"YDPO9Awd",{},[],"Bush's machine will not, of course, be built exactly as he foresaw. The complete description, which I omitted, involves microfilm cas¬ settes, a photographic copying plate for adding new images to the microfilm file, and a telautograph stylus. Other machines he describes, such as the forehead camera and the direct-dictation typing machine, might or might not have been coupled to it as well. In the revised version of the article (5) his emphasis shifted to videotape. These impedimenta we ignore. There exist microfilm cassettes, copiers and so on, but the hardware ready to support a memex-class system will be something else.",{"_31":9911,"_33":9912},[],{"_35":160,"_37":9913,"_39":663,"_41":9914,"_66":9915,"_68":9916,"_70":69},"uhwoRLHW",{},[],"The system will be built from existing computer equipment and peripherals. Physically it will be a computer display, with a keyboard, at the user's desk; a support computer system (at the desk or elsewhere) for handling various technical chores; and a library network of digital feeder machines. The written materials, when not shown on the screen, will be stored and sent digitally, as telegraphic symbolg.’They will be sent back and forth among these systems automatically, as programmed in the various devices. The trails, or associative text structures—more generally called \"hypertexts\"—will be stored in coded form, along with, the more conventional documents in the various devices. The user will be billed automatically for the services and the delivery of copyrighted materials. The publisher, who maintains these copyrighted materials in the feeder machines, will be duly paid for their use.",{"_31":9918,"_33":9919},[],{"_35":160,"_37":9920,"_39":663,"_41":9921,"_66":9922,"_68":9923,"_70":69},"rjFINwnJ",{},[],"Prototype units exist now. Appropriate console hardware can be purchased now for about $15,000.",{"_31":9925,"_33":9926},[],{"_35":160,"_37":9927,"_39":663,"_41":9928,"_66":9929,"_68":9930,"_70":69},"MpSmGT1C",{},[],"Supply systems, however, are not quite ready. The best supply system may be a special-purpose computer or a general-purpose time¬ sharing pyitem; which is better is not clear. While costs of either are presently in thi tSAB or hundreds of thousands, they are coming down fast, and the use of a well-tailored system by many people at once should bring down the cost of such service down considerably. To name a figure arbitrarily, let us say that a service cost of $100 a month per user (exclusive of telephone lines and copyright) would be suffi¬ ciently low to draw many users. Such service at such a cost will surely be generally available between one and five years from now.",{"_31":9932,"_33":9933},[],{"_35":160,"_37":9934,"_39":663,"_41":9935,"_66":9936,"_68":9937,"_70":69},"kZrOy0ql",{},[],"Various preoccupations have delayed us psychologically. We do not need direct dictation, optical scanning or the availability (sic) of vast libraries for such systems to be immediately practical and important to us.",{"_35":870,"_37":9939,"_39":663,"_41":9940,"_66":9941,"_68":9942,"_70":69},"M0VjGRF0",{"_273":323},[],"Transposition",{"_31":9944,"_33":10043},[9945,9952,9959,9966,9973,9980,9987,9994,10001,10015,10022,10029,10036],{"_31":9946,"_33":9947},[],{"_35":160,"_37":9948,"_39":663,"_41":9949,"_66":9950,"_68":9951,"_70":69},"yRCt0hCQ",{},[],"We are speaking of a single console to handle notes, writing, much correspondence, much reading, and the creation of new kinds of texts. On it the user must be able to view, edit, file, and otherwise manipulate.",{"_31":9953,"_33":9954},[],{"_35":160,"_37":9955,"_39":663,"_41":9956,"_66":9957,"_68":9958,"_70":69},"uD8XLQ64",{},[],"Let me now describe a system for various kinds of text handling, the Xanadu Parallel Textface™. XANADU™ is a system presently under development as a turnkey computer graphics console for non-technical users. A stand-alone system, it is built on a minicomputer with disk and / or cassette tape, vectoring display screen, and keyboard. A variety of unusual programming techniques permit various types of screen animation, as well as automatic retrieval and data-base editing in the undersystem; these automatically service different user front ends, faces or theaters. Foremost among these theaters is the Parallel Textface, a text system of some power and delicacy.",{"_31":9960,"_33":9961},[],{"_35":160,"_37":9962,"_39":663,"_41":9963,"_66":9964,"_68":9965,"_70":69},"30jJW2pE",{},[],"Many of its features exist in other text handling systems, notably that of Douglas C. Engelbart at Stanford Research Institute (6). The purpose of this description is to show parallelisms between memex and this general type of system, not to distinguish this system from its relatives.",{"_31":9967,"_33":9968},[],{"_35":160,"_37":9969,"_39":663,"_41":9970,"_66":9971,"_68":9972,"_70":69},"60pYAt72",{},[],"I will speak of the Xanadu hypertext system, or Parallel Textface, simply as \"the system,\" \"the current system\" or the like, to distinguish it from the memex. As its implementation is not yet complete, this description applies to the present specifications and not only the parts that are working. We will note some resemblances to the memex.",{"_31":9974,"_33":9975},[],{"_35":160,"_37":9976,"_39":663,"_41":9977,"_66":9978,"_68":9979,"_70":69},"nALZJw6b",{},[],"The user sits at a display screen with a typewriter keyboard, a light pen or other pointing tool, and various optional controls. With these he may read, explore, annotate, write and revise. Storage is of course digital rather than pictorial; the system may manipulate the words letter by letter, rather than as a single image.",{"_31":9981,"_33":9982},[],{"_35":160,"_37":9983,"_39":663,"_41":9984,"_66":9985,"_68":9986,"_70":69},"wnSELNQB",{},[],"In basic editorial operations, the system presents text materials on the screen; the user may command basic writing and editing actions by simple manipulations. Indeed, he may make these editorial changes tentatively, on copies or alternative versions of the material; and he may, at his option, have his actions recorded automatically in a cumu¬ lative editorial log, in case it is later necessary to retract any of them.",{"_31":9988,"_33":9989},[],{"_35":160,"_37":9990,"_39":663,"_41":9991,"_66":9992,"_68":9993,"_70":69},"Yf16Esb5",{},[],"Bush did not really go into memex editorial operations, but of course there was that keyboard. It is interesting to note that the memex described in the revised version of Bush's article (5) kept a log of manipulations by the user. (95-6)",{"_31":9995,"_33":9996},[],{"_35":160,"_37":9997,"_39":663,"_41":9998,"_66":9999,"_68":10000,"_70":69},"GTnHIVqA",{},[],"The system is generally geared to tentative and thoughtful opera¬ tion. The alternative versions and editorial log are the strongest ex¬ amples, but there are others. An editing command may be retracted if its results do not please. Another example: a section of text being tried in a new place is shown glowing more brightly, so you know its limits within the new setting.",{"_31":10002,"_33":10010},[10003],{"_31":10004,"_33":10005},[],{"_35":160,"_37":10006,"_39":663,"_41":10007,"_66":10008,"_68":10009,"_70":69},"DUCET99r",{},[],"In the memex, the user could skip through a document at adjustable rates (107, col. 1, para. 5). In the current system he may zip forward through the text at whatever speed he chooses, watching it slide on the screen. (The necessity of smooth, incremental text motion for the CRT is not yet generally recognized.)",{"_35":160,"_37":10011,"_39":663,"_41":10012,"_66":10013,"_68":10014,"_70":69},"Jg93zaTs",{"_273":323},[],"The user of Bush's memex called its contents by means of a \"code book\" (107 passim )—but this too was actually stored in the system. From the code book the user was to choose contents for yiewing^with a single tap of the key,\" as mentioned earlier. In the current system it is possible lor the user to call something to the screen by picking the name from a screen menu or relational diagram with the light pen. Fie may do this not just with whole units, but also with subparts and different ver- v sions—separate copies—of documents being tentatively edited.",{"_31":10016,"_33":10017},[],{"_35":160,"_37":10018,"_39":663,"_41":10019,"_66":10020,"_68":10021,"_70":69},"lmCgmnpX",{},[],"The memex user looked at several documents simultaneously through several screens or panels of the same screen (107, col. 1, para, 6). This simultaneous viewing will be possible for several documents on the Parallel Textface; indeed, explicit linkages between associated texts may be viewed on request. This is the notion of \"parallel text,\" useful for commentaries, translations, intercomparisons of documents and much else. These facilities correspond rather well, I think, to Bush's \"marginal notes and comments\" between the \"several projection posi¬ tions.\"",{"_31":10023,"_33":10024},[],{"_35":160,"_37":10025,"_39":663,"_41":10026,"_66":10027,"_68":10028,"_70":69},"twmc1uQQ",{},[],"The memex user created annotations by hand, or links between the things that were being viewed simultaneously. This is possible on the current system, which allows the user to create links between text sections regardless of whether or not they are parts of the same unit or otherwise related. These may be between parallel texts, or among free- floating paragraphs (discrete or \"free\" hypertexts), or in virtually any other useful arrangement.",{"_31":10030,"_33":10031},[],{"_35":160,"_37":10032,"_39":663,"_41":10033,"_66":10034,"_68":10035,"_70":69},"PC4fPpfg",{},[],"For any system of this kind, design problems arise in the richer operations, such as creating and modifying connective structures. It is taken for granted that the console must be easy to use. That is no design problem for a small set of operations, such as text editing. But the design of the overall file handling elements and actions is more complicated. There are two problems. The first is how to achieve the desired perfor¬ mance values on available equipment and accepted software setting. This becomes a tradeoff. The grander problem, though, is conceptual unification for the system's filing structure and conventions.",{"_31":10037,"_33":10038},[],{"_35":160,"_37":10039,"_39":663,"_41":10040,"_66":10041,"_68":10042,"_70":69},"_pEfIwrZ",{},[],"In the current system there is presently only one type of connector. This restriction nevertheless permits a system sufficient to support real hypertext experimentation. Complex or annotated couplings are pres¬ ently not defined. However, simple links are adequate for various possible forms of discrete-jump hypertexts, including Bush trails, and may in principle be extended to computer responsibility for link behav¬ iors and complex coupling maintenance.",{"_35":870,"_37":10044,"_39":663,"_41":10045,"_66":10046,"_68":10047,"_70":69},"LXMJugTL",{"_273":323},[],"The Console",{"_31":10049,"_33":10190},[10050,10057,10071,10085,10099,10113,10120,10127,10134,10141,10148,10155,10162,10169,10176,10183],{"_31":10051,"_33":10052},[],{"_35":160,"_37":10053,"_39":663,"_41":10054,"_66":10055,"_68":10056,"_70":69},"0WEyivCC",{},[],"While Bush's term, \"trail,\" represents a very useful concept, we must generalize it. Bush's interest in microfilm led to his idea of the trail having a sequence.",{"_31":10058,"_33":10066},[10059],{"_31":10060,"_33":10061},[],{"_35":160,"_37":10062,"_39":663,"_41":10063,"_66":10064,"_68":10065,"_70":69},"qf_cC4Y7",{},[],"For [the user] runs through an encyclopedia, finds an interesting but sketchy article, leaves it projected. Next, in a history, he finds another pertinent item, and ties the two together. Thus he goes, building a trail of many items. (107, col. 2, para. 4)",{"_35":160,"_37":10067,"_39":663,"_41":10068,"_66":10069,"_68":10070,"_70":69},"10j2-4ds",{"_273":323},[],"By \"trail,\" Bush appears to have meant a sequence of document*^ document excerpts, and comment! upon them.",{"_31":10072,"_33":10080},[10073],{"_31":10074,"_33":10075},[],{"_35":160,"_37":10076,"_39":663,"_41":10077,"_66":10078,"_68":10079,"_70":69},"5sDzzO17",{},[],"When the user is building a trail, he names it, inserts the name in his code book, and taps it out on his keyboard. Before him are the two items to be joined projected onto adjacent viewing positions.... The user taps a single key, and the items are permanently joined. (107, col. 2, para. 2)",{"_35":160,"_37":10081,"_39":663,"_41":10082,"_66":10083,"_68":10084,"_70":69},"9C9AlJI6",{"_273":323},[],"This sequence would be established by making paired couplings.",{"_31":10086,"_33":10094},[10087],{"_31":10088,"_33":10089},[],{"_35":160,"_37":10090,"_39":663,"_41":10091,"_66":10092,"_68":10093,"_70":69},"dV1QbUyB",{},[],"Occasionally he inserts a comment of his own, either linking it into the main trail or joining it by a side trail to a particular item.",{"_35":160,"_37":10095,"_39":663,"_41":10096,"_66":10097,"_68":10098,"_70":69},"soA09eVb",{"_273":323},[],"Bush mentions two other types of trail. One is the \"side trail,\" branching out from a main trail sequence.",{"_31":10100,"_33":10108},[10101],{"_31":10102,"_33":10103},[],{"_35":160,"_37":10104,"_39":663,"_41":10105,"_66":10106,"_68":10107,"_70":69},"eOeFvpiI",{},[],"The historian, with a vast chronological account of a people, parallels it with a skip trail which stops only on the salient items, and can follow at any time contemporary trails which lead him all over civilization at a particular epoch. (108, col. 1, para. 1)",{"_35":160,"_37":10109,"_39":663,"_41":10110,"_66":10111,"_68":10112,"_70":69},"T_Dc-elN",{"_273":323},[],"The other type of trail is the \"skip trail,\" a subset of a main trail sequence that contains the highlights.",{"_31":10114,"_33":10115},[],{"_35":160,"_37":10116,"_39":663,"_41":10117,"_66":10118,"_68":10119,"_70":69},"YHIk647s",{},[],"In Bush's trails, the user had no choices to make as he moved through the sequence of items, except at an intersection of trails. With computer storage, however, no sequence need be imposed on the material; and, instead of simply storing materials in their order of arrival or of being noticed, it will be possible to create overall structures of greater useful? complexity. These may have, for instance, patterns of branches in various directions. Such non-sequential or complex text structures we may call \"hypertexts.\" (7)",{"_31":10121,"_33":10122},[],{"_35":160,"_37":10123,"_39":663,"_41":10124,"_66":10125,"_68":10126,"_70":69},"UfB8V-Sg",{},[],"\"Hypertext\" is the generic term; there are reasons, for which there Is no room here, to rule out such other candidate terms as \"branching text,\" \"graph-structured text,\" \"complex text\" and \"tree text.\"",{"_31":10128,"_33":10129},[],{"_35":160,"_37":10130,"_39":663,"_41":10131,"_66":10132,"_68":10133,"_70":69},"QOoVSIEq",{},[],"The best current definition of hypertext, over quite a broad range of types, is \"text Structure that cannot be conveniently printed.\" This is not very specific profound, but it fits best.",{"_31":10135,"_33":10136},[],{"_35":160,"_37":10137,"_39":663,"_41":10138,"_66":10139,"_68":10140,"_70":69},"-AGQ1NP9",{},[],"As Bush pointed out in his own terms, we think in hypertext (106, col. 2). We have been speaking hypertext all our lives and never known it. It is usually only in writing that we must pick thoughts up and irrelevantly put them down in the sequence demanded by the printed word. Writing is a process of making the tree of thought into a picket fence.",{"_31":10142,"_33":10143},[],{"_35":160,"_37":10144,"_39":663,"_41":10145,"_66":10146,"_68":10147,"_70":69},"hP34F12B",{},[],"Hypertext structures are varied. For instance, they may be free- branching with only one type of link and backing up; they may have modal links with different meanings in a free structure; or have modal links and repetitive structure.",{"_31":10149,"_33":10150},[],{"_35":160,"_37":10151,"_39":663,"_41":10152,"_66":10153,"_68":10154,"_70":69},"hhxI_GYs",{},[],"Discrete-jump hypertexts are not the only kinds. There is, for example. Stretchtext™. This is continuously variable text which never leaves the screen, but changes by small increments on user demand, growing longer and more detailed by a few words at a time, as required. Other continuous types are possible.",{"_31":10156,"_33":10157},[],{"_35":160,"_37":10158,"_39":663,"_41":10159,"_66":10160,"_68":10161,"_70":69},"3nvTs9mC",{},[],"Just as items may be coupled, whole hypertexts may be coupled into books, or one another. An example of the first would be a hypertext with annotations coupling into the Bible. Such multi-couplings involve bundles of pointers between the texts, possibly with type codes or annotations. (In the current system the non-annotated multicoupler is the canonical case between files.) They may also involve alternative versions, which there is no room to discuss here. The structuring of these coupler types is a continuing design task for hypertext systems.",{"_31":10163,"_33":10164},[],{"_35":160,"_37":10165,"_39":663,"_41":10166,"_66":10167,"_68":10168,"_70":69},"uLC2cmbX",{},[],"The creator of hypertexts may allow the user various options of jumping or branching. These options can lead the user to further reading in any pattern the author wants to make available to him. The only constraints on the author are usefulness, clarity, and artfulness.",{"_31":10170,"_33":10171},[],{"_35":160,"_37":10172,"_39":663,"_41":10173,"_66":10174,"_68":10175,"_70":69},"VZneRGrL",{},[],"There must, of course, be ways the reader may see, and choose among, possible branches from an item in the text. This problem was | implicit in Bush's treatment. Since \"any item can be joined into numer¬ ous trails\" (107, col. 2, para. 3) there would have had to be some way of j showing the user these options and their meaning. This is the case in] general, and a standing aspect of hypertext system design.",{"_31":10177,"_33":10178},[],{"_35":160,"_37":10179,"_39":663,"_41":10180,"_66":10181,"_68":10182,"_70":69},"iYPj_x-O",{},[],"Hypertexts may be casual rough notes, as described in Bush'l extended example of the Turkish bow and arrow; or they may at th@| other extreme be finished units, editorially completed and organized* Such finished units would have many of the same properties as binary writing: intentional assembly, attempted clarity and expository structure of enumerable \"points,\" and an overall comprehensible pat¬ tern whose interrelated parts may be in some way remembered or visualized. Finally, the concept of authorship applies to hypertexts as much as it does to an ordinary book or article.",{"_31":10184,"_33":10185},[],{"_35":160,"_37":10186,"_39":663,"_41":10187,"_66":10188,"_68":10189,"_70":69},"MXn38uto",{},[],"As with ordinary texts, too, the editorial properties and \"feel\" of hypertexts may be quite distinct and varied. For hypertexts these are of course largely unexplored. It is also very hard to anticipate their possible administrative and social settings, and this will greatly affect their character and the modes of their use.",{"_35":870,"_37":10191,"_39":663,"_41":10192,"_66":10193,"_68":10194,"_70":69},"EsLzTZeo",{"_273":323},[],"Hypertexts",{"_31":10196,"_33":10218},[10197,10211],{"_31":10198,"_33":10206},[10199],{"_31":10200,"_33":10201},[],{"_35":160,"_37":10202,"_39":663,"_41":10203,"_66":10204,"_68":10205,"_70":69},"4MeAzRck",{},[],"The network will consist of several computers or computer-like objects. In the user's own unit is digital logic, and possibly (as in our Xanadu) a small computer; if not, this unit is serviced or managed by a computer which stores the user's files and communicates with the library network. The user's requests for documents that are not avail¬ able locally go out to a library network. These requests are sorted out to the appropriate repository machine; the repository machine returns the document and a bill or fee schedule.",{"_35":160,"_37":10207,"_39":663,"_41":10208,"_66":10209,"_68":10210,"_70":69},"2q33hgDx",{"_273":323},[],"A general transmission network will carry requested documents from libraries to users, new documents from users to libraries, and commu¬ nications and documents between users.",{"_31":10212,"_33":10213},[],{"_35":160,"_37":10214,"_39":663,"_41":10215,"_66":10216,"_68":10217,"_70":69},"RzHgKXEU",{},[],"Various fees are logged up to the user. These will include various basic costs, such as membership in the system, rental of the terminal and hookup. Additional fees may include logged-in time, per-usage costs of s ' various facilities (such as average memory area occupied and quanti¬ ties of text moved), storage charges for materials kept locally, and royalties to copyright holders. It should be noted that various grades of service may also exist, in which the user gets faster service by claiming larger buffers and higher priorities, and pays for the privilege.",{"_35":870,"_37":10219,"_39":663,"_41":10220,"_66":10221,"_68":10222,"_70":69},"2uctG9Ee",{"_273":323},[],"The Transmission Network",{"_31":10224,"_33":10225},[],{"_35":160,"_37":10226,"_39":663,"_41":10227,"_66":10228,"_68":10229,"_70":69},"Z34QbOfh",{},[],"A1 though this may sound like a formidable prospect, in general and with polishing there is reason to hope that the real costs of such a system will compete favorably with the real costs of the forms of publication and libraries we now employ. (Of course, in such \"real cost\" we must include the library services supplied \"free\" by various levels of govern¬ ment, including municipal libraries, grants to universities and the indirect subsidy of publishers by low postal rates. It is not unthinkable that similar encouragement will come about for this form of publishing and libraryship.)",{"_31":10231,"_33":10232},[],{"_35":160,"_37":10233,"_39":663,"_41":10234,"_66":10235,"_68":10236,"_70":69},"goBmMxuA",{},[],"Various technical design issues exist. These involve the feeder computers and their forms of memory. These hierarchies of memory are fairly clear. They will generally include disk (for working areas and directories), magnetic card or data cell (for the corpus), and magnetic tape (for rarely-needed materials and safety copies). Immense solid- state memories will never take over completely unless they are cheaper.",{"_31":10238,"_33":10239},[],{"_35":160,"_37":10240,"_39":663,"_41":10241,"_66":10242,"_68":10243,"_70":69},"GsGw4htV",{},[],"A more difficult question is, what should the feeder computers be? Their job in this system is the lookup and shovelling of text, plus book¬ keeping. One school of thought holds that a true general-purpose time¬ sharing system is necessary; another, that the correct machine is a dedicated computer with rich interrupts and comparatively little arith¬ metic capacity. The third school would point out the special character of the work and lean toward special designs and special tradeoffs, which could be anything from associative memory to the use of delay¬ line machines.",{"_31":10245,"_33":10246},[],{"_35":160,"_37":10247,"_39":663,"_41":10248,"_66":10249,"_68":10250,"_70":69},"zbAVqPyW",{},[],"Similar issues exist for memory software and directory systems. There are complex technical problems of index and search techniques, and methods of their cross-tabulation. But they can be handled in some way or other.",{"_31":10252,"_33":10253},[],{"_35":160,"_37":10254,"_39":663,"_41":10255,"_66":10256,"_68":10257,"_70":69},"krHVUmbv",{},[],"A warning is necessary here, however. This area of console support is the area where things are not yet ready. The prediction of economic feasibility in five years, an eon in the computer world, is not the same as feasibility now. By devoting a whole computer, disk and tape to each user, the problem of console support can now be solved, in a manner of speaking; but the general problem of interleaved I/O and file manage¬ ment, with the efficient sharing of facilities, is another problem entirely, and the one that must be solved to make this whole thing go.",{"_31":10259,"_33":10288},[10260,10267,10274,10281],{"_31":10261,"_33":10262},[],{"_35":160,"_37":10263,"_39":663,"_41":10264,"_66":10265,"_68":10266,"_70":69},"HvU5_0F7",{},[],"Bush regarded his new text structures as transmissible between indi¬ viduals, and publishable. The same is true of hypertext units, the generalized form of trails. I think it likely that once such systems are available, the creation of branching and complex text will become recognized as far more natural than the structures in which we now must write.",{"_31":10268,"_33":10269},[],{"_35":160,"_37":10270,"_39":663,"_41":10271,"_66":10272,"_68":10273,"_70":69},"NpJlNMMo",{},[],"This will all follow naturally from the existence of consoles which permit multiple couplings between texts. Having created for personal use a hyper-document on one's console, it will seem only reasonable to press a button passing this on to a colleague in its hyper-form, without chopping and aligning it into conventional writing.",{"_31":10275,"_33":10276},[],{"_35":160,"_37":10277,"_39":663,"_41":10278,"_66":10279,"_68":10280,"_70":69},"GqUvfyXk",{},[],"Various interesting possibilities follow. Private \"journals\" in a field may be started among co-workers merely by the pooling of their hyper¬ documents. The rental of memory space on magnetic cards is inconse¬ quential next to what have been the costs of printing and mailing.",{"_31":10282,"_33":10283},[],{"_35":160,"_37":10284,"_39":663,"_41":10285,"_66":10286,"_68":10287,"_70":69},"Xfwi21W4",{},[],"When professional and technical societies become interested in sponsoring hyper-publication, one of the most straightforward ways to begin would be with the creation of society-sponsored review articles. These could be like the ordinary review articles sponsored by such societies, save that the review article would open directly into the various materials it was reviewing, and footnotes could be more extensive and slanted to different categories of reader. (Eigure 1.)",{"_35":870,"_37":10289,"_39":663,"_41":10290,"_66":10291,"_68":10292,"_70":69},"6C-tIuHJ",{"_273":323},[],"Publication: Redesign of the Technical Literature",{"_31":10294,"_33":10295},[],{"_35":1875,"_37":10296,"_39":663,"_41":10297,"_66":10298,"_68":69,"_70":10299},"AHdU7Sic",{"_273":323},[],"ipfs://bafkreih45rwplfyhtcvhvhoartio23fr3nw6m6j376tdi4zwetqeytmcde",{"_31":10301,"_33":10302},[],{"_35":160,"_37":10303,"_39":663,"_41":10304,"_66":10305,"_68":10306,"_70":69},"4N2-B8DE",{},[],"The next step is, of course, the creation of hyper-magazines or journals under the sponsorship and supervision of professional societ¬ ies. Here the problem of organization would seem to become thorny. But this collection could be much like the journals of today, except for the direct availability of previous literature, working papers and vari¬ ous odds and ends. It should be observed that any of the \"documents\" noted in the illustration can themselves be hypertexts. (Figure 2.)",{"_31":10308,"_33":10309},[],{"_35":1875,"_37":10310,"_39":663,"_41":10311,"_66":10312,"_68":69,"_70":10313},"xZqgbKwl",{"_273":323},[],"ipfs://bafkreidg4wc4cvzvp7m3e4gvxyultgcikkm5staxbf6ziywff5s6mxmuzm",{"_31":10315,"_33":10316},[],{"_35":160,"_37":10317,"_39":663,"_41":10318,"_66":10319,"_68":10320,"_70":69},"RCYxK8Fa",{},[],"In this magazine, an arbitrary conjecture, all material of the past year is considered \"recent\" and embraced in a common lookup struc¬ ture. New material enters the collection surreptitiously, at whatever time of day or night the editors release it; material one year old is formally expelled to a different file on the first of each month. (It may be just as accessible, but its nominal status changes, rather like that of a book taken off the \"recent acquisitions\" list of a library.) This maga¬ zine would hold most of what people were talking about in a field, and it would all be right there.",{"_31":10322,"_33":10323},[],{"_35":160,"_37":10324,"_39":663,"_41":10325,"_66":10326,"_68":10327,"_70":69},"PTfKOL8e",{},[],"There are numerous technical complications to hypertext publish¬ ing. There is no room here to discuss the more esoteric technical ones, such as facilities, billing and copyright conventions, or possible techniques of encryption and validation to prevent pirating of works and to authenticate expeditionary versions.",{"_31":10329,"_33":10379},[10330,10337,10344,10351,10358,10365,10372],{"_31":10331,"_33":10332},[],{"_35":160,"_37":10333,"_39":663,"_41":10334,"_66":10335,"_68":10336,"_70":69},"JTmcgPSS",{},[],"How shall it begin?",{"_31":10338,"_33":10339},[],{"_35":160,"_37":10340,"_39":663,"_41":10341,"_66":10342,"_68":10343,"_70":69},"AeoACfTd",{},[],"Those contemplating massive retrieval systems commonly pre¬ sume that they must begin with some massive corpus all accessible. The Library of Congress is often mentioned. Even Bush supposes regret¬ fully (in the revised article, p. 100) that the personal system waits on large public establishments being automated first.",{"_31":10345,"_33":10346},[],{"_35":160,"_37":10347,"_39":663,"_41":10348,"_66":10349,"_68":10350,"_70":69},"odGms8KE",{},[],"I do not believe this is so. It will be practicable and of considerable interest to begin on a small scale, having no grand corpus available. The grand corpus will come soon enough, as requests emerge. (We have a precedent: the prowess of University Microfilms, Inc. in rendering texts available to scholars in microfilm.)",{"_31":10352,"_33":10353},[],{"_35":160,"_37":10354,"_39":663,"_41":10355,"_66":10356,"_68":10357,"_70":69},"EDQvrf0V",{},[],"The way to begin is to furnish supported consoles to small commu¬ nities of users: key members of a \"small\" discipline, or specialists among whose work there is close connection. Suitable groups might be \"early Egyptologists,\" or just plain \"everybody at Woods Hole.\"",{"_31":10359,"_33":10360},[],{"_35":160,"_37":10361,"_39":663,"_41":10362,"_66":10363,"_68":10364,"_70":69},"2ov65eVP",{},[],"Such communicants, having been assured as well as possible of privacy and fail-safe design, will be encouraged to use the consoles fully. From the outset they may keep all their notes, manuscripts, articles, and copies of outgoing correspondence, on the system.",{"_31":10366,"_33":10367},[],{"_35":160,"_37":10368,"_39":663,"_41":10369,"_66":10370,"_68":10371,"_70":69},"gJRQI_G-",{},[],"The rest will follow. I am fairly sure of the predictions so far, at least in broad outline, but I am just as sure that the first generation of hypertext users will invent twice as much as has been descried and described so far.",{"_31":10373,"_33":10374},[],{"_35":160,"_37":10375,"_39":663,"_41":10376,"_66":10377,"_68":10378,"_70":69},"JGwiEpx3",{},[],"Who will support these beginnings? We have a choice, at the outset, of universities, publishing companies, computer companies (including service bureaux), research organizations or the government. Any of these might take such an initiative. Though such an initiative would seem severally unthinkable, it somehow seems collectively plausible and, of course, historically inevitable. If you believe in manifest destiny.",{"_35":870,"_37":10380,"_39":663,"_41":10381,"_66":10382,"_68":10383,"_70":69},"NmPbmZbl",{"_273":323},[],"How to Begin",{"_31":10385,"_33":10386},[],{"_35":160,"_37":10387,"_39":663,"_41":10388,"_66":10389,"_68":10390,"_70":69},"FqdZj537",{},[],"Theodor H. Nelson",{"_31":10392,"_33":10442},[10393,10400,10407,10414,10421,10428,10435],{"_31":10394,"_33":10395},[],{"_35":160,"_37":10396,"_39":663,"_41":10397,"_66":10398,"_68":10399,"_70":69},"q7BCIKoH",{},[],"Vannevar Bush, “As We May Think.\" The Atlantic Monthly 176:1 (July, 1945), 101-108. References to \"Bush\" cite this article unless further specified, and all unexplained numbers and paginations in the text refer to it. Because the article is so tightly written and our interest in it so close, paginations are given to the column and paragraph.",{"_31":10401,"_33":10402},[],{"_35":160,"_37":10403,"_39":663,"_41":10404,"_66":10405,"_68":10406,"_70":69},"BAYej_AG",{},[],"Allen Kent, Textbook on Mechanized Information Retrieval , second edition. Wiley, 1966; pp. 7-9.",{"_31":10408,"_33":10409},[],{"_35":160,"_37":10410,"_39":663,"_41":10411,"_66":10412,"_68":10413,"_70":69},"Knny6v2L",{},[],"Joseph Becker and Robert M. Hayes, Information Storage and Retrieval: Tools, Elements, Theories. Wiley, 1963; p. 40.",{"_31":10415,"_33":10416},[],{"_35":160,"_37":10417,"_39":663,"_41":10418,"_66":10419,"_68":10420,"_70":69},"FCyi95T7",{},[],"John H. Wilson, \"As We May Have Thought.\" In Progress in Information Science and Technology: Proceedings of the American Documentation Institute 1966 Annual Meeting. Adrianne Press, 1966, pp. 117-122.",{"_31":10422,"_33":10423},[],{"_35":160,"_37":10424,"_39":663,"_41":10425,"_66":10426,"_68":10427,"_70":69},"OiWtgN5T",{},[],"Vannevar Bush, \"Memex Revisited.\" In Vannevar Bush, Science Is Not Enough. William Morrow and Company, Inc., 1967, 75-101.",{"_31":10429,"_33":10430},[],{"_35":160,"_37":10431,"_39":663,"_41":10432,"_66":10433,"_68":10434,"_70":69},"-cs1mRKO",{},[],"Douglas C. Engelbart, \"Augmenting Human Intellect: A Conceptual Framework.\" AFOSR-3223 Summary Report, Stanford Research Institute, Menlo Park, California, October 1962. This expresses the philosophy, rather than the results, of the continuing project.",{"_31":10436,"_33":10437},[],{"_35":160,"_37":10438,"_39":663,"_41":10439,"_66":10440,"_68":10441,"_70":69},"mzUjEM1v",{},[],"Theodor H. Nelson, \"Getting It Out of Our System.\" In George Schechter (ed.). Information Retrieval: A Critical View. Thompson Book Company, 1967; pp. 191-210.",{"_35":870,"_37":10443,"_39":663,"_41":10444,"_66":10445,"_68":10446,"_70":69},"ojtCZdE_",{"_273":2113},[],"Endnotes",[279],"/records/as-we-will-think",{"_82":683},{},{"_37":660,"_95":53,"_54":10452,"_71":663,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,662],1772031973214,[149,660,663],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/as-we-will-think\",\"bafy2bzacecch5uwnt26x7dklj2wsiozscxmqoyev5may4dvqmc6nb5kqhly7k\"]",{"_110":10457,"_147":10954,"_150":10955},{"_112":10458,"_131":132,"_133":10953,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":10459,"_37":10951},{"_28":10460,"_71":689,"_72":53,"_73":10946,"_54":10947,"_76":698,"_78":10948,"_80":10949,"_84":10950,"_86":699,"_88":89},[10461,10473,10485,10506,10554,10596,10645,10673,10687,10736,10750,10764,10869,10897,10911,10925],{"_31":10462,"_33":10463},[],{"_35":160,"_37":10464,"_39":699,"_41":10465,"_66":10466,"_68":10472,"_70":69},"wUSPjXYl",{},[10467],{"_35":204,"_167":10468,"_169":10469,"_41":10470,"_70":10471},[5843],[5591],{},"mailto:ted@xanadu.net","Theodor Holm Nelson Project Xanadu, Keio University and University of Southampton e-mail ted@xanadu.net",{"_31":10474,"_33":10475},[],{"_35":160,"_37":10476,"_39":699,"_41":10477,"_66":10478,"_68":10484,"_70":69},"Bp4Qfhbi",{},[10479],{"_35":204,"_167":10480,"_169":10481,"_41":10482,"_70":10483},[2828],[6479],{},"https://xanadu.com.au/ted/transcopyright/transcopy.html","Origin Server: https://xanadu.com.au/ted/transcopyright/transcopy.html",{"_31":10486,"_33":10501},[10487,10494],{"_31":10488,"_33":10489},[],{"_35":160,"_37":10490,"_39":699,"_41":10491,"_66":10492,"_68":10493,"_70":69},"dsozFF9o",{},[],"The on-line copyright problem may be resolvable by a simple, sweeping permission method. This proposed system, which anyone may use, allows broad re-use of materials in exchange for automatic tracking of ownership. Payment goes to the original publisher and credit to the original author. Nothing is misquoted, nothing is out of context (since the original context is immediately available), and users are not spied upon.",{"_31":10495,"_33":10496},[],{"_35":160,"_37":10497,"_39":699,"_41":10498,"_66":10499,"_68":10500,"_70":69},"3OXCe6Vl",{},[],"A wording and an abbreviation for this permission system are proposed here.",{"_35":870,"_37":10502,"_39":699,"_41":10503,"_66":10504,"_68":10505,"_70":69},"jNijcoDR",{"_273":323},[],"SUMMARY",{"_31":10507,"_33":10550},[10508,10515,10522,10529,10536,10543],{"_31":10509,"_33":10510},[],{"_35":160,"_37":10511,"_39":699,"_41":10512,"_66":10513,"_68":10514,"_70":69},"brZRn_iR",{},[],"Someone who asks, \"How do we keep people from stealing food?\" is asking you to consider only his side of the issue, without addressing underlying problems. But it might be sensible to ask another question in reply. If we ask, \"How can the people obtain food?\", perhaps both problems can be solved together.",{"_31":10516,"_33":10517},[],{"_35":160,"_37":10518,"_39":699,"_41":10519,"_66":10520,"_68":10521,"_70":69},"8EZ1ioFl",{},[],"That is how I see the issue of copyright in digital media. Those who merely ask, \"How do we prevent copyright infringement?\" are only asking the first question without addressing the second. There is a hunger for the re-use of media. If we can find a legitimate way to feed this hunger, then perhaps the stealing will not be necessary.",{"_31":10523,"_33":10524},[],{"_35":160,"_37":10525,"_39":699,"_41":10526,"_66":10527,"_68":10528,"_70":69},"Xpb7W3Jw",{},[],"Today's central controversy seems to be the question of how to manage copyright and royalty on the sale of digital content.",{"_31":10530,"_33":10531},[],{"_35":160,"_37":10532,"_39":699,"_41":10533,"_66":10534,"_68":10535,"_70":69},"H9Qs7d23",{},[],"The standard question has been, \"How do we prevent infringement?\" If we re-frame the question as \"How can we allow re-use?\", the solution may be simpler and more powerful than everyone thinks, with benefits for everyone.",{"_31":10537,"_33":10538},[],{"_35":160,"_37":10539,"_39":699,"_41":10540,"_66":10541,"_68":10542,"_70":69},"PbgLCTXr",{},[],"This reformulates an idea which occurred to the author in the fall of 1960, and which since then has been an implicit part of the Xanadu Project (1), an ambitious system of hypermedia publishing servers with deep version management. Because the project has been controversial and beset with difficulties, our fundamental copyright proposal was not understood. And because this method was embedded in the software that had been designed for the Xanadu project, it was not recognized or expounded as a separate legal permission doctrine.",{"_31":10544,"_33":10545},[],{"_35":160,"_37":10546,"_39":699,"_41":10547,"_66":10548,"_68":10549,"_70":69},"1hIDT9H4",{},[],"In this paper, we now separate that copyright method from its software history, and present it as a method anyone can use. It is a legal permission doctrine with far-reaching consequences, whose benefits may be considerable.",{"_35":870,"_37":10551,"_39":699,"_41":10552,"_66":10553,"_68":5929,"_70":69},"k25R4mHO",{"_273":323},[],{"_31":10555,"_33":10591},[10556,10563,10570,10577,10584],{"_31":10557,"_33":10558},[],{"_35":160,"_37":10559,"_39":699,"_41":10560,"_66":10561,"_68":10562,"_70":69},"cacNULNT",{},[],"From the beginning, the objective of Project Xanadu was to facilitate a new kind of literature: a new populist medium, a many-to-many publishing system, not centralized in editorial and publishing companies, but open to anyone. It was intended to create a new kind of freedom of the press, and make possible a deeper understanding of published materials (2).",{"_31":10564,"_33":10565},[],{"_35":160,"_37":10566,"_39":699,"_41":10567,"_66":10568,"_68":10569,"_70":69},"0HgU8n3a",{},[],"But this would not mean simply electronic availability of closed documents; we would also need to re-use existing materials, and the computer could help keep this re-use orderly (and do so without spying on users).",{"_31":10571,"_33":10572},[],{"_35":160,"_37":10573,"_39":699,"_41":10574,"_66":10575,"_68":10576,"_70":69},"qUVkCHlD",{},[],"The idea was to preserve integrity, copyright and royalty for digital materials, yet allow everyone freely to re-use these materials, which would retain their identity at all times. By allowing everyone to republish all materials, this would effectively define a new system of fluid, digital transmedia, with universal freedom of re-use and visualization. All different republications could in principle be viewed side-by-side by the user, thus leading to greater understanding of the material and of the points of view of the different documents, their authors and republishers.",{"_31":10578,"_33":10579},[],{"_35":160,"_37":10580,"_39":699,"_41":10581,"_66":10582,"_68":10583,"_70":69},"zElpS3C7",{},[],"The scheme is simple: under this arrangement, everyone is free to republish digital materials virtually, as quotations, anthologies and collages, provided that the republication is virtual: that is, provided that the republisher only provides instructions for acquisiton and assembly of the parts, and each copy of previously-published bytes is separately purchased from the original publisher(s) at the time of delivery. A republisher only distributes pointers showing how to obtain the material, and in what new context(s) to place the material; each recipient buys these materials independently.",{"_31":10585,"_33":10586},[],{"_35":160,"_37":10587,"_39":699,"_41":10588,"_66":10589,"_68":10590,"_70":69},"PI0YivhU",{},[],"This method provides each receiving party with a properly-owned, independent copy of the materials, all purchased anew from the original publisher. What may be just as important, it provides incentives for participation and a method for honest re-use in a system from which all benefit.",{"_35":870,"_37":10592,"_39":699,"_41":10593,"_66":10594,"_68":10595,"_70":69},"4Ub9rpVm",{"_273":323},[],"THE OBJECTIVE",{"_31":10597,"_33":10640},[10598,10605,10612],{"_31":10599,"_33":10600},[],{"_35":160,"_37":10601,"_39":699,"_41":10602,"_66":10603,"_68":10604,"_70":69},"-yWOcfjN",{},[],"What is proposed here turns out actually to be, at its center, a permission doctrine. A new permission doctrine may be easily added to our culture; a variety of permission doctrines are already popular, such as \"shareware\" and \"all rights reserved, except that churches may reprint freely.\"",{"_31":10606,"_33":10607},[],{"_35":160,"_37":10608,"_39":699,"_41":10609,"_66":10610,"_68":10611,"_70":69},"uEIMiZkC",{},[],"In this proposed permission doctrine, the copyright holder gives permission for republication, PROVIDED THAT the material is sent to users only as an address for the material being republished, indicating what material is to be included in what new context, and inviting the recipient to purchase the content bytes anew from their present publisher. When a recipient purchases material, the material is sent with identifiers as to its origin; and the user has software enabling these identifiers to be kept. This has a number of benefits: (1) the user knows the origin; (2) this identification can be part of a proof of purchase; (3) in principle, any recipient may republish in the same fashion, ad infinitum.",{"_31":10613,"_33":10635},[10614,10621,10628],{"_31":10615,"_33":10616},[],{"_35":160,"_37":10617,"_39":699,"_41":10618,"_66":10619,"_68":10620,"_70":69},"ZxDNZyym",{},[],"To allow this, the copyright holder must therefore make a statement like the following. (Note that I am still tinkering with the provisions and wording.)",{"_31":10622,"_33":10623},[],{"_35":160,"_37":10624,"_39":699,"_41":10625,"_66":10626,"_68":10627,"_70":69},"rjEqzKKo",{},[],"\"Permission is granted to all parties in the universe to re-publish the bytes of these materials virtually in new on-line contexts, provided (1) that such virtual republication consists of transmitting only a purchase address for bytes to be included in a particular new context; and provided (2) that the present publisher is notified of any such virtual republication.\"",{"_31":10629,"_33":10630},[],{"_35":160,"_37":10631,"_39":699,"_41":10632,"_66":10633,"_68":10634,"_70":69},"c572Na4t",{},[],"This may be adequate to achieve the desired result, as we will consider below. It also leaves room for a number of possible variations.",{"_35":870,"_37":10636,"_39":699,"_41":10637,"_66":10638,"_68":10639,"_70":69},"S4F01bwb",{"_273":323},[],"LONG FORM PERMISSION",{"_35":870,"_37":10641,"_39":699,"_41":10642,"_66":10643,"_68":10644,"_70":69},"7zCGLn1a",{"_273":323},[],"A PERMISSION DOCTRINE",{"_31":10646,"_33":10668},[10647,10654,10661],{"_31":10648,"_33":10649},[],{"_35":160,"_37":10650,"_39":699,"_41":10651,"_66":10652,"_68":10653,"_70":69},"JgpmeBjp",{},[],"This may seem over-simple, when mighty technical and legislative solutions are being sought by so many parties. But it shifts the ground of the issue.",{"_31":10655,"_33":10656},[],{"_35":160,"_37":10657,"_39":699,"_41":10658,"_66":10659,"_68":10660,"_70":69},"_T72pSmK",{},[],"The new ground becomes the issue of CONTEXT RELINQUISHMENT-- the publisher's willingness to allow the material to be used in unpredictable contexts, in return for royalty, credit, and the immediate availability of the original contexts for further purchase, inspection and comparison.",{"_31":10662,"_33":10663},[],{"_35":160,"_37":10664,"_39":699,"_41":10665,"_66":10666,"_68":10667,"_70":69},"Y7mOKd7e",{},[],"This is a tradeoff. We expect publishers-- especially small, non-traditional publishers and self-publishing individuals-- to be invigorated by the notion of their materials being available for universal sale and re-use, to their benefit. More traditional publishers and authors may hesitate, not recognizing that all the traditional objectives may be satisfied by this system.",{"_35":870,"_37":10669,"_39":689,"_41":10670,"_66":10671,"_68":10672,"_70":69},"3lBM7vjq",{"_273":323},[],"IRONICALLY SIMPLE",{"_31":10674,"_33":10682},[10675],{"_31":10676,"_33":10677},[],{"_35":160,"_37":10678,"_39":699,"_41":10679,"_66":10680,"_68":10681,"_70":69},"kB1Aa5RP",{},[],"Implied in this method are certain other aspects of implementation. For instance, the user must be given a receipt for each portion purchased, so that the received materials may be proved a legitimate copy. A survivable memorandum of origin (the address from which purchased) must also accompany the repurchased materials, making virtual republication possible once again (by the new recipient). And the republisher must notify the original publisher of the republication, so that these re-uses may be seen.",{"_35":870,"_37":10683,"_39":689,"_41":10684,"_66":10685,"_68":10686,"_70":69},"6OGEE3Ci",{"_273":323},[],"IMPLIED ASPECTS",{"_31":10688,"_33":10731},[10689,10696,10703],{"_31":10690,"_33":10691},[],{"_35":160,"_37":10692,"_39":699,"_41":10693,"_66":10694,"_68":10695,"_70":69},"MNPJQJFL",{},[],"This permission doctrine has certain minimal requirements for supporting software. Certain unusual software features are required:",{"_31":10697,"_33":10698},[],{"_35":160,"_37":10699,"_39":699,"_41":10700,"_66":10701,"_68":10702,"_70":69},"BadN2E0x",{},[],"Server-side software: The server program should have the ability to sell materials in small amounts, ideally at a fixed price per byte, delivering the materials with a receipt and identity notification.",{"_31":10704,"_33":10726},[10705,10712,10719],{"_31":10706,"_33":10707},[],{"_35":160,"_37":10708,"_39":699,"_41":10709,"_66":10710,"_68":10711,"_70":69},"AUjNyGTG",{},[],"Viewer program with purchase methods. Any recipient must have a viewer program (\"client software\") which has methods for purchasing the required bytes, and which retains the identity of bytes purchased.",{"_31":10713,"_33":10714},[],{"_35":160,"_37":10715,"_39":699,"_41":10716,"_66":10717,"_68":10718,"_70":69},"zycMiC4Z",{},[],"Editing program which retains identities of portions. Any republisher must have an editing program which retains the original identity and addresses of the edited materials, even as they become cut down (or re-expanded by additional purchases from the original).",{"_31":10720,"_33":10721},[],{"_35":160,"_37":10722,"_39":699,"_41":10723,"_66":10724,"_68":10725,"_70":69},"ZQjsNs0y",{},[],"Stripping program. After an author has finished creating a document which is to include republished material, a special stripping program (or feature) must then prepare the document for skeleton transmission, stripping out the actual bytes and substituting the original addresses in the necessary format for their repurchase.",{"_35":160,"_37":10727,"_39":699,"_41":10728,"_66":10729,"_68":10730,"_70":69},"t2lJAIkY",{"_273":2113},[],"Client-side software: Certain detailed features of an unusual nature are required in the user's programs.",{"_35":870,"_37":10732,"_39":689,"_41":10733,"_66":10734,"_68":10735,"_70":69},"J9i9eU_d",{"_273":323},[],"SUPPORTING SOFTWARE ASPECTS",{"_31":10737,"_33":10745},[10738],{"_31":10739,"_33":10740},[],{"_35":160,"_37":10741,"_39":699,"_41":10742,"_66":10743,"_68":10744,"_70":69},"ME9QYzcC",{},[],"The recipient who purchases the suggested materials owns a final copy, like any book, each portion legally purchased. Even if the materials are later withdrawn from sale, each copy already acquired in this way retains itsownership status as the possession of the recipient.",{"_35":870,"_37":10746,"_39":699,"_41":10747,"_66":10748,"_68":10749,"_70":69},"e7yTOty9",{"_273":323},[],"OWNERSHIP OF EACH FINAL COPY",{"_31":10751,"_33":10759},[10752],{"_31":10753,"_33":10754},[],{"_35":160,"_37":10755,"_39":699,"_41":10756,"_66":10757,"_68":10758,"_70":69},"2pX_wpkQ",{},[],"Note that any party may offer transcopyright; and note that different variations of this arrangement, with different details of availability, may be mixed and matched in a given document (see below). Regardless of such variations, a legitimate mixed copy is still owned by the final recipient.",{"_35":870,"_37":10760,"_39":699,"_41":10761,"_66":10762,"_68":10763,"_70":69},"rUXNmxua",{"_273":323},[],"COMPATIBILITY, INTEROPERABILITY",{"_31":10765,"_33":10864},[10766,10780,10794,10801,10822,10829,10843,10850,10857],{"_31":10767,"_33":10775},[10768],{"_31":10769,"_33":10770},[],{"_35":160,"_37":10771,"_39":699,"_41":10772,"_66":10773,"_68":10774,"_70":69},"sg7lckfk",{},[],"Trans(c)(year)(name)",{"_35":160,"_37":10776,"_39":699,"_41":10777,"_66":10778,"_68":10779,"_70":69},"ZMkNa8Vv",{"_273":323},[],"I propound for this permission system an extremely simple presentational format. A publisher signifies participation by the following notice, in the place of the usual copyright notice:",{"_31":10781,"_33":10789},[10782],{"_31":10783,"_33":10784},[],{"_35":160,"_37":10785,"_39":699,"_41":10786,"_66":10787,"_68":10788,"_70":69},"Kk5z_3XQ",{},[],"Trans(c)1995 Irving Snerd",{"_35":160,"_37":10790,"_39":699,"_41":10791,"_66":10792,"_68":10793,"_70":69},"-bPhCN80",{"_273":323},[],"For example,",{"_31":10795,"_33":10796},[],{"_35":160,"_37":10797,"_39":699,"_41":10798,"_66":10799,"_68":10800,"_70":69},"7LetWbRi",{},[],"This is a shorthand form of the long-form permission stated earlier, so that the publisher is spared having to include it.",{"_31":10802,"_33":10817},[10803,10810],{"_31":10804,"_33":10805},[],{"_35":160,"_37":10806,"_39":699,"_41":10807,"_66":10808,"_68":10809,"_70":69},"NCVZnjvY",{},[],"Trans(c)1995 Irving Snerd; administered Dun & Bradstreet. or",{"_31":10811,"_33":10812},[],{"_35":160,"_37":10813,"_39":699,"_41":10814,"_66":10815,"_68":10816,"_70":69},"POtByzif",{},[],"Ziff-Davis Trans(c)1995 Irving Snerd.",{"_35":160,"_37":10818,"_39":699,"_41":10819,"_66":10820,"_68":10821,"_70":69},"NknvdOv4",{"_273":323},[],"Some distribution agency or availability scheme should also be specified by the transcopyright grantor, as, for example:",{"_31":10823,"_33":10824},[],{"_35":160,"_37":10825,"_39":699,"_41":10826,"_66":10827,"_68":10828,"_70":69},"AyuJBVD2",{},[],"Either of these notifications tells all parties, in condensed form, (1) that copyright is claimed; (2) that transcopyright permission is granted, and (3) where the materials may be bought.",{"_31":10830,"_33":10838},[10831],{"_31":10832,"_33":10833},[],{"_35":160,"_37":10834,"_39":699,"_41":10835,"_66":10836,"_68":10837,"_70":69},"7q56R-FM",{},[],"(c)1995 Irving Snerd ",{"_35":160,"_37":10839,"_39":699,"_41":10840,"_66":10841,"_68":10842,"_70":69},"zijiMGdS",{"_273":323},[],"It will be noted that the traditional copyright notice",{"_31":10844,"_33":10845},[],{"_35":160,"_37":10846,"_39":699,"_41":10847,"_66":10848,"_68":10849,"_70":69},"YqM6RY5K",{},[],"is FULLY CONTAINED within the transcopyright notice, and so is still present.",{"_31":10851,"_33":10852},[],{"_35":160,"_37":10853,"_39":699,"_41":10854,"_66":10855,"_68":10856,"_70":69},"ELhVQqkv",{},[],"However, note also that this traditional copyright notice no longer has its former force in law, since by today's law an author now establishes copyright automatically by creating a work; so the copyright notice is now regarded as being a courtesy and a convenience. Thus we are offering the transcopyright permission as a further courtesy, so that all parties will know how they may republish.",{"_31":10858,"_33":10859},[],{"_35":160,"_37":10860,"_39":699,"_41":10861,"_66":10862,"_68":10863,"_70":69},"vzY1PYHG",{},[],"By what authority is this a shorthand of the longer version? I hereby DECLARE it to be such a shorthand form, just as the terms \"shareware\" and \"copyleft,\" declared by Bob Wallace and Richard Stallman respectively, have come to represent their respective permission doctrines, both now widely accepted and used. If others use the transcopyright notification with the intent given here, it will be recognized in law (like shareware and copyleft) as being synonymous with the longer permission notice.",{"_35":870,"_37":10865,"_39":699,"_41":10866,"_66":10867,"_68":10868,"_70":69},"r6q50lI0",{"_273":323},[],"THE PROPOSED FORMAT AND ITS LEGAL STATUS",{"_31":10870,"_33":10892},[10871,10878,10885],{"_31":10872,"_33":10873},[],{"_35":160,"_37":10874,"_39":699,"_41":10875,"_66":10876,"_68":10877,"_70":69},"jV9vaJYf",{},[],"This arrangement is for on-line screen viewing and keepage of digital data, not for paper or other solid media.",{"_31":10879,"_33":10880},[],{"_35":160,"_37":10881,"_39":699,"_41":10882,"_66":10883,"_68":10884,"_70":69},"epwXZiCC",{},[],"A number of issues are not handled by this arrangement. These include byte modification (such as morphing, bytewise graphical operations, and merged re-use of audio samples into a fused, mixed, inseparable recording). It does not involve printout. It does not cover site licensing for multiple users. It does not include model releases, talent releases, or other forms of permission not strictly part of copyright. It does not state how long materials will be offered for sale.",{"_31":10886,"_33":10887},[],{"_35":160,"_37":10888,"_39":699,"_41":10889,"_66":10890,"_68":10891,"_70":69},"JBbARtK1",{},[],"Who settles these details? This is within the scope of variation of the idea: different forms of transcopyright may be offered by different parties-- individuals, companies, or other administrations. Any party offering transcopyright may bundle different kinds of permission into their own systems. (For instance, the contracts of Project Xanadu will have specific clauses with respect to length of availability, paper printout and site licensing.)",{"_35":870,"_37":10893,"_39":699,"_41":10894,"_66":10895,"_68":10896,"_70":69},"nxKFA0cQ",{"_273":323},[],"VARIATIONS NOT COVERED; DIFFERENT JURISDICTIONS",{"_31":10898,"_33":10906},[10899],{"_31":10900,"_33":10901},[],{"_35":160,"_37":10902,"_39":699,"_41":10903,"_66":10904,"_68":10905,"_70":69},"bP2HSJYk",{},[],"This system is not automatically enforced, but neither is any other feasible electronic copyright system. It is no more or less enforceable than any other. The fact that it defines a convenient method for honest behavior, satisfying principal objectives of both publisher and republisher-- no longer \"infringer,\" but honest participant-- is a strong argument in its favor.",{"_35":870,"_37":10907,"_39":699,"_41":10908,"_66":10909,"_68":10910,"_70":69},"gifi-l5O",{"_273":323},[],"ENFORCEMENT AND BENEFITS",{"_31":10912,"_33":10920},[10913],{"_31":10914,"_33":10915},[],{"_35":160,"_37":10916,"_39":699,"_41":10917,"_66":10918,"_68":10919,"_70":69},"FZl1ZfTd",{},[],"My special thanks to Robert W. Fiddler, Esq., of Great Neck, N.Y., for over twenty-five years of friendship, generous legal tutoring, and delightful banter that have helped shape these ideas; but any errors, misunderstandings, or improprieties are my own.",{"_35":870,"_37":10921,"_39":699,"_41":10922,"_66":10923,"_68":10924,"_70":69},"1LGgTbce",{"_273":323},[],"ACKNOWLEDGMENT",{"_31":10926,"_33":10941},[10927,10934],{"_31":10928,"_33":10929},[],{"_35":160,"_37":10930,"_39":699,"_41":10931,"_66":10932,"_68":10933,"_70":69},"H0MET-YY",{},[],"Nelson, Theodor Holm, Literary Machines. Available from Mindful Press, 3020 Bridgeway #295, Sausalito, CA 94965, USA.",{"_31":10935,"_33":10936},[],{"_35":160,"_37":10937,"_39":699,"_41":10938,"_66":10939,"_68":10940,"_70":69},"M116WUdG",{},[],"Nelson, Theodor Holm, \"Literature Unified by Transclusion.\" Communications of the ACM, 1995.\n",{"_35":870,"_37":10942,"_39":699,"_41":10943,"_66":10944,"_68":10945,"_70":69},"LaCO6csZ",{"_273":2113},[],"BIBLIOGRAPHY",[279],"/records/transcopyright-pre-permission-for-virtual-republishing","2025-04-22T13:16:59.245Z",{"_82":712},{},{"_37":686,"_95":53,"_54":10952,"_71":689,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,688],1772031973285,[149,686,689],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/transcopyright-pre-permission-for-virtual-republishing\",\"bafy2bzaceclc5nlpgulmjwhnqelgtmzn4ulwy64vercqapqvs7f7m6tshknfm\"]",{"_110":10957,"_147":11619,"_150":11620},{"_112":10958,"_131":132,"_133":11618,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":10959,"_37":11616},{"_28":10960,"_71":718,"_72":53,"_73":11611,"_54":11612,"_76":726,"_78":11613,"_80":11614,"_84":11615,"_86":727,"_88":89},[10961,10973,10985,10997,11003,11010,11017,11024,11116,11219,11303,11345,11422,11492,11534],{"_31":10962,"_33":10963},[],{"_35":160,"_37":10964,"_39":10965,"_41":10966,"_66":10967,"_68":10972,"_70":69},"LT8SR8VG","bafy2bzacectcr6tbm6lphxz6qevqdzbf5b6l2tri4gq4huw5drbp3vtxk2326",{},[10968],{"_35":166,"_167":10969,"_169":10970,"_41":10971,"_70":69},[5591],[7296],{},"“Consider a future device … in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility. It is an enlarged intimate supplement to his memory.”",{"_31":10974,"_33":10975},[],{"_35":160,"_37":10976,"_39":10965,"_41":10977,"_66":10978,"_68":10984,"_70":69},"PUjhoPGO",{},[10979],{"_35":204,"_167":10980,"_169":10981,"_41":10982,"_70":10983},[46],[1488],{},"undefined","By Vannevar Bush",{"_31":10986,"_33":10987},[],{"_35":160,"_37":10988,"_39":10965,"_41":10989,"_66":10990,"_68":10996,"_70":69},"jHU9XtzX",{},[10991],{"_35":204,"_167":10992,"_169":10993,"_41":10994,"_70":10995},[6982],[6448],{},"hm://z6MkrbYsRzKb1VABdvhsDSAk6JK8fAszKsyHhcaZigYeWCou/keywords?v=bafy2bzacebmjuozpxuj7gz5xopm7bcqql3wrsuvtxwex3myzvynb4vrsa7r3q#hEOcMm4d","Keywords: Keywords",{"_31":10998,"_33":10999},[],{"_35":1875,"_37":11000,"_39":10965,"_41":11001,"_66":11002,"_68":69,"_70":737},"_moUTRZu",{},[],{"_31":11004,"_33":11005},[],{"_35":160,"_37":11006,"_39":10965,"_41":11007,"_66":11008,"_68":11009,"_70":69},"h5EzPleN",{},[],"This has not been a scientist's war; it has been a war in which all have had a part. The scientists, burying their old professional competition in the demand of a common cause, have shared greatly and learned much. It has been exhilarating to work in effective partnership. Now, for many, this appears to be approaching an end. What are the scientists to do next?",{"_31":11011,"_33":11012},[],{"_35":160,"_37":11013,"_39":10965,"_41":11014,"_66":11015,"_68":11016,"_70":69},"7bq1agtk",{},[],"For the biologists, and particularly for the medical scientists, there can be little indecision, for their war has hardly required them to leave the old paths. Many indeed have been able to carry on their war research in their familiar peacetime laboratories. Their objectives remain much the same. WOW",{"_31":11018,"_33":11019},[],{"_35":160,"_37":11020,"_39":10965,"_41":11021,"_66":11022,"_68":11023,"_70":69},"vaq59NuB",{},[],"It is the physicists who have been thrown most violently off stride, who have left academic pursuits for the making of strange destructive gadgets, who have had to devise new methods for their unanticipated assignments. They have done their part on the devices that made it possible to turn back the enemy, have worked in combined effort with the physicists of our allies. They have felt within themselves the stir of achievement. They have been part of a great team. Now, as peace approaches, one asks where they will find objectives worthy of their best.",{"_31":11025,"_33":11111},[11026,11034,11041,11048,11067,11074,11081,11088,11095],{"_31":11027,"_33":11028},[],{"_35":160,"_37":11029,"_39":11030,"_41":11031,"_66":11032,"_68":11033,"_70":69},"fsvLRbpM","bafy2bzaceb7xb4ixpk4kzd73mql3ogwmak26fcc3plf35sbrxmr7lzh3drfyw",{},[],"Of what lasting benefit has been man’s use of science and of the new instruments which his research brought into existence? First, they have increased his control of his material environment. They have improved his food, his clothing, his shelter; they have increased his security and released him partly from the bondage of bare existence. They have given him increased knowledge of his own biological processes so that he has had a progressive freedom from disease and an increased span of life. They are illuminating the interactions of his physiological and psychological functions, giving the promise of an improved mental health.",{"_31":11035,"_33":11036},[],{"_35":160,"_37":11037,"_39":11030,"_41":11038,"_66":11039,"_68":11040,"_70":69},"FtyqstGP",{},[],"Science has provided the swiftest communication between individuals; it has provided a record of ideas and has enabled man to manipulate and to make extracts from that record so that knowledge evolves and endures throughout the life of a race rather than that of an individual.",{"_31":11042,"_33":11043},[],{"_35":160,"_37":11044,"_39":11030,"_41":11045,"_66":11046,"_68":11047,"_70":69},"EtPB8OOn",{},[],"There is a growing mountain of research. But there is increased evidence that we are being bogged down today as specialization extends. The investigator is staggered by the findings and conclusions of thousands of other workers—conclusions which he cannot find time to grasp, much less to remember, as they appear. Yet specialization becomes increasingly necessary for progress, and the effort to bridge between disciplines is correspondingly superficial.",{"_31":11049,"_33":11050},[],{"_35":160,"_37":11051,"_39":11030,"_41":11052,"_66":11053,"_68":11066,"_70":69},"ElkdsWEh",{},[11054,11061],{"_35":204,"_167":11055,"_169":11057,"_41":11059,"_70":11060},[11056],594,[11058],610,{},"https://www.theatlantic.com/magazine/archive/2016/06/genes-are-overrated/480729/",{"_35":11062,"_167":11063,"_169":11064,"_41":11065,"_70":69},"Underline",[11056],[11058],{},"Professionally our methods of transmitting and reviewing the results of research are generations old and by now are totally inadequate for their purpose. If the aggregate time spent in writing scholarly works and in reading them could be evaluated, the ratio between these amounts of time might well be startling. Those who conscientiously attempt to keep abreast of current thought, even in restricted fields, by close and continuous reading might well shy away from an examination calculated to show how much of the previous month’s efforts could be produced on call. Mendel’s concept of the laws of genetics was lost to the world for a generation because his publication did not reach the few who were capable of grasping and extending it; and this sort of catastrophe is undoubtedly being repeated all about us, as truly significant attainments become lost in the mass of the inconsequential.",{"_31":11068,"_33":11069},[],{"_35":160,"_37":11070,"_39":11030,"_41":11071,"_66":11072,"_68":11073,"_70":69},"_X828seC",{},[],"The difficulty seems to be, not so much that we publish unduly in view of the extent and variety of present day interests, but rather that publication has been extended far beyond our present ability to make real use of the record. The summation of human experience is being expanded at a prodigious rate, and the means we use for threading through the consequent maze to the momentarily important item is the same as was used in the days of square-rigged ships.",{"_31":11075,"_33":11076},[],{"_35":160,"_37":11077,"_39":11030,"_41":11078,"_66":11079,"_68":11080,"_70":69},"UulAaPMh",{},[],"But there are signs of a change as new and powerful instrumentalities come into use. Photocells capable of seeing things in a physical sense, advanced photography which can record what is seen or even what is not, thermionic tubes capable of controlling potent forces under the guidance of less power than a mosquito uses to vibrate his wings, cathode ray tubes rendering visible an occurrence so brief that by comparison a microsecond is a long time, relay combinations which will carry out involved sequences of movements more reliably than any human operator and thousands of times as fast—there are plenty of mechanical aids with which to effect a transformation in scientific records.",{"_31":11082,"_33":11083},[],{"_35":160,"_37":11084,"_39":11030,"_41":11085,"_66":11086,"_68":11087,"_70":69},"CQCC_MuI",{},[],"Two centuries ago Leibnitz invented a calculating machine which embodied most of the essential features of recent keyboard devices, but it could not then come into use. The economics of the situation were against it: the labor involved in constructing it, before the days of mass production, exceeded the labor to be saved by its use, since all it could accomplish could be duplicated by sufficient use of pencil and paper. Moreover, it would have been subject to frequent breakdown, so that it could not have been depended upon; for at that time and long after, complexity and unreliability were synonymous.",{"_31":11089,"_33":11090},[],{"_35":160,"_37":11091,"_39":11030,"_41":11092,"_66":11093,"_68":11094,"_70":69},"kvppvgUU",{},[],"Babbage, even with remarkably generous support for his time, could not produce his great arithmetical machine. His idea was sound enough, but construction and maintenance costs were then too heavy. Had a Pharaoh been given detailed and explicit designs of an automobile, and had he understood them completely, it would have taxed the resources of his kingdom to have fashioned the thousands of parts for a single car, and that car would have broken down on the first trip to Giza.",{"_31":11096,"_33":11097},[],{"_35":160,"_37":11098,"_39":11030,"_41":11099,"_66":11100,"_68":11110,"_70":69},"rW1JcTwl",{},[11101,11106],{"_35":204,"_167":11102,"_169":11103,"_41":11104,"_70":11105},[7150],[6317],{},"https://www.theatlantic.com/technology/archive/2013/09/the-hidden-world-of-the-typewriter/279523/",{"_35":11062,"_167":11107,"_169":11108,"_41":11109,"_70":69},[7150],[6317],{},"Machines with interchangeable parts can now be constructed with great economy of effort. In spite of much complexity, they perform reliably. Witness the humble typewriter, or the movie camera, or the automobile. Electrical contacts have ceased to stick when thoroughly understood. Note the automatic telephone exchange, which has hundreds of thousands of such contacts, and yet is reliable. A spider web of metal, sealed in a thin glass container, a wire heated to brilliant glow, in short, the thermionic tube of radio sets, is made by the hundred million, tossed about in packages, plugged into sockets—and it works! Its gossamer parts, the precise location and alignment involved in its construction, would have occupied a master craftsman of the guild for months; now it is built for thirty cents. The world has arrived at an age of cheap complex devices of great reliability; and something is bound to come of it.",{"_35":870,"_37":11112,"_39":11030,"_41":11113,"_66":11114,"_68":11115,"_70":69},"-6w4sC-U",{"_273":323},[],"1",{"_31":11117,"_33":11214},[11118,11125,11132,11139,11146,11153,11160,11167,11174,11181,11188,11201],{"_31":11119,"_33":11120},[],{"_35":160,"_37":11121,"_39":11030,"_41":11122,"_66":11123,"_68":11124,"_70":69},"SRZ0vATy",{},[],"A record if it is to be useful to science, must be continuously extended, it must be stored, and above all it must be consulted. Today we make the record conventionally by writing and photography, followed by printing; but we also record on film, on wax disks, and on magnetic wires. Even if utterly new recording procedures do not appear, these present ones are certainly in the process of modification and extension.",{"_31":11126,"_33":11127},[],{"_35":160,"_37":11128,"_39":11030,"_41":11129,"_66":11130,"_68":11131,"_70":69},"2c3C7fi7",{},[],"Certainly progress in photography is not going to stop. Faster material and lenses, more automatic cameras, finer-grained sensitive compounds to allow an extension of the minicamera idea, are all imminent. Let us project this trend ahead to a logical, if not inevitable, outcome. The camera hound of the future wears on his forehead a lump a little larger than a walnut. It takes pictures 3 millimeters square, later to be projected or enlarged, which after all involves only a factor of 10 beyond present practice. The lens is of universal focus, down to any distance accommodated by the unaided eye, simply because it is of short focal length. There is a built-in photocell on the walnut such as we now have on at least one camera, which automatically adjusts exposure for a wide range of illumination. There is film in the walnut for a hundred exposures, and the spring for operating its shutter and shifting its film is wound once for all when the film clip is inserted. It produces its result in full color. It may well be stereoscopic, and record with two spaced glass eyes, for striking improvements in stereoscopic technique are just around the corner.",{"_31":11133,"_33":11134},[],{"_35":160,"_37":11135,"_39":11030,"_41":11136,"_66":11137,"_68":11138,"_70":69},"pdVl6vYY",{},[],"The cord which trips its shutter may reach down a man’s sleeve within easy reach of his fingers. A quick squeeze, and the picture is taken. On a pair of ordinary glasses is a square of fine lines near the top of one lens, where it is out of the way of ordinary vision. When an object appears in that square, it is lined up for its picture. As the scientist of the future moves about the laboratory or the field, every time he looks at something worthy of the record, he trips the shutter and in it goes, without even an audible click. Is this all fantastic? The only fantastic thing about it is the idea of making as many pictures as would result from its use.",{"_31":11140,"_33":11141},[],{"_35":160,"_37":11142,"_39":11030,"_41":11143,"_66":11144,"_68":11145,"_70":69},"Om8w7cZv",{},[],"Will there be dry photography? It is already here in two forms. When Brady made his Civil War pictures, the plate had to be wet at the time of exposure. Now it has to be wet during development instead. In the future perhaps it need not be wetted at all. There have long been films impregnated with diazo dyes which form a picture without development, so that it is already there as soon as the camera has been operated. An exposure to ammonia gas destroys the unexposed dye, and the picture can then be taken out into the light and examined. The process is now slow, but someone may speed it up, and it has no grain difficulties such as now keep photographic researchers busy. Often it would be advantageous to be able to snap the camera and to look at the picture immediately.",{"_31":11147,"_33":11148},[],{"_35":160,"_37":11149,"_39":11030,"_41":11150,"_66":11151,"_68":11152,"_70":69},"GYpDNHoP",{},[],"Another process now in use is also slow, and more or less clumsy. For fifty years impregnated papers have been used which turn dark at every point where an electrical contact touches them, by reason of the chemical change thus produced in an iodine compound included in the paper. They have been used to make records, for a pointer moving across them can leave a trail behind. If the electrical potential on the pointer is varied as it moves, the line becomes light or dark in accordance with the potential.",{"_31":11154,"_33":11155},[],{"_35":160,"_37":11156,"_39":11030,"_41":11157,"_66":11158,"_68":11159,"_70":69},"uhEJCqrR",{},[],"This scheme is now used in facsimile transmission. The pointer draws a set of closely spaced lines across the paper one after another. As it moves, its potential is varied in accordance with a varying current received over wires from a distant station, where these variations are produced by a photocell which is similarly scanning a picture. At every instant the darkness of the line being drawn is made equal to the darkness of the point on the picture being observed by the photocell. Thus, when the whole picture has been covered, a replica appears at the receiving end.",{"_31":11161,"_33":11162},[],{"_35":160,"_37":11163,"_39":11030,"_41":11164,"_66":11165,"_68":11166,"_70":69},"KtGcS1nr",{},[],"A scene itself can be just as well looked over line by line by the photocell in this way as can a photograph of the scene. This whole apparatus constitutes a camera, with the added feature, which can be dispensed with if desired, of making its picture at a distance. It is slow, and the picture is poor in detail. Still, it does give another process of dry photography, in which the picture is finished as soon as it is taken.",{"_31":11168,"_33":11169},[],{"_35":160,"_37":11170,"_39":11030,"_41":11171,"_66":11172,"_68":11173,"_70":69},"VomN4nAf",{},[],"It would be a brave man who would predict that such a process will always remain clumsy, slow, and faulty in detail. Television equipment today transmits sixteen reasonably good pictures a second, and it involves only two essential differences from the process described above. For one, the record is made by a moving beam of electrons rather than a moving pointer, for the reason that an electron beam can sweep across the picture very rapidly indeed. The other difference involves merely the use of a screen which glows momentarily when the electrons hit, rather than a chemically treated paper or film which is permanently altered. This speed is necessary in television, for motion pictures rather than stills are the object.",{"_31":11175,"_33":11176},[],{"_35":160,"_37":11177,"_39":11030,"_41":11178,"_66":11179,"_68":11180,"_70":69},"t1EgGQs2",{},[],"Use chemically treated film in place of the glowing screen, allow the apparatus to transmit one picture only rather than a succession, and a rapid camera for dry photography results. The treated film needs to be far faster in action than present examples, but it probably could be. More serious is the objection that this scheme would involve putting the film inside a vacuum chamber, for electron beams behave normally only in such a rarefied environment. This difficulty could be avoided by allowing the electron beam to play on one side of a partition, and by pressing the film against the other side, if this partition were such as to allow the electrons to go through perpendicular to its surface, and to prevent them from spreading out sideways. Such partitions, in crude form, could certainly be constructed, and they will hardly hold up the general development.",{"_31":11182,"_33":11183},[],{"_35":160,"_37":11184,"_39":11030,"_41":11185,"_66":11186,"_68":11187,"_70":69},"K1L6Vnfe",{},[],"Like dry photography, microphotography still has a long way to go. The basic scheme of reducing the size of the record, and examining it by projection rather than directly, has possibilities too great to be ignored. The combination of optical projection and photographic reduction is already producing some results in microfilm for scholarly purposes, and the potentialities are highly suggestive. Today, with microfilm, reductions by a linear factor of 20 can be employed and still produce full clarity when the material is re-enlarged for examination. The limits are set by the graininess of the film, the excellence of the optical system, and the efficiency of the light sources employed. All of these are rapidly improving.",{"_31":11189,"_33":11190},[],{"_35":160,"_37":11191,"_39":11030,"_41":11192,"_66":11193,"_68":11200,"_70":69},"tAiERhgM",{},[11194],{"_35":919,"_167":11195,"_169":11197,"_41":11199,"_70":69},[11196],288,[11198],311,{},"Assume a linear ratio of 100 for future use. Consider film of the same thickness as paper, although thinner film will certainly be usable. Even under these conditions there would be a total factor of 10,000 between the bulk of the ordinary record on books, and its microfilm replica. The Encyclopædia Britannica could be reduced to the volume of a matchbox. A library of a million volumes could be compressed into one end of a desk. If the human race has produced since the invention of movable type a total record, in the form of magazines, newspapers, books, tracts, advertising blurbs, correspondence, having a volume corresponding to a billion books, the whole affair, assembled and compressed, could be lugged off in a moving van. Mere compression, of course, is not enough; one needs not only to make and store a record but also be able to consult it, and this aspect of the matter comes later. Even the modern great library is not generally consulted; it is nibbled at by a few.",{"_31":11202,"_33":11203},[],{"_35":160,"_37":11204,"_39":11030,"_41":11205,"_66":11206,"_68":11213,"_70":69},"hhWzhvhy",{},[11207],{"_35":919,"_167":11208,"_169":11210,"_41":11212,"_70":69},[9541,11209],324,[6533,11211],334,{},"Compression is important, however, when it comes to costs. The material for the microfilm Britannica would cost a nickel, and it could be mailed anywhere for a cent. What would it cost to print a million copies? To print a sheet of newspaper, in a large edition, costs a small fraction of a cent. The entire material of the Britannica in reduced microfilm form would go on a sheet eight and one-half by eleven inches. Once it is available, with the photographic reproduction methods of the future, duplicates in large quantities could probably be turned out for a cent apiece beyond the cost of materials. The preparation of the original copy? That introduces the next aspect of the subject.",{"_35":870,"_37":11215,"_39":11030,"_41":11216,"_66":11217,"_68":11218,"_70":69},"_TGEPVNw",{"_273":323},[],"2",{"_31":11220,"_33":11298},[11221,11228,11235,11242,11249,11256,11263,11270,11277,11284,11291],{"_31":11222,"_33":11223},[],{"_35":160,"_37":11224,"_39":11030,"_41":11225,"_66":11226,"_68":11227,"_70":69},"mcSU_1Z4",{},[],"To make the record, we now push a pencil or tap a typewriter. Then comes the process of digestion and correction, followed by an intricate process of typesetting, printing, and distribution. To consider the first stage of the procedure, will the author of the future cease writing by hand or typewriter and talk directly to the record? He does so indirectly, by talking to a stenographer or a wax cylinder; but the elements are all present if he wishes to have his talk directly produce a typed record. All he needs to do is to take advantage of existing mechanisms and to alter his language.",{"_31":11229,"_33":11230},[],{"_35":160,"_37":11231,"_39":11030,"_41":11232,"_66":11233,"_68":11234,"_70":69},"e1OnZ5ys",{},[],"At a recent World Fair a machine called a Voder was shown. A girl stroked its keys and it emitted recognizable speech. No human vocal chords entered into the procedure at any point; the keys simply combined some electrically produced vibrations and passed these on to a loud-speaker. In the Bell Laboratories there is the converse of this machine, called a Vocoder. The loudspeaker is replaced by a microphone, which picks up sound. Speak to it, and the corresponding keys move. This may be one element of the postulated system.",{"_31":11236,"_33":11237},[],{"_35":160,"_37":11238,"_39":11030,"_41":11239,"_66":11240,"_68":11241,"_70":69},"3_IW5nwv",{},[],"The other element is found in the stenotype, that somewhat disconcerting device encountered usually at public meetings. A girl strokes its keys languidly and looks about the room and sometimes at the speaker with a disquieting gaze. From it emerges a typed strip which records in a phonetically simplified language a record of what the speaker is supposed to have said. Later this strip is retyped into ordinary language, for in its nascent form it is intelligible only to the initiated. Combine these two elements, let the Vocoder run the stenotype, and the result is a machine which types when talked to.",{"_31":11243,"_33":11244},[],{"_35":160,"_37":11245,"_39":11030,"_41":11246,"_66":11247,"_68":11248,"_70":69},"3APnJbW5",{},[],"Our present languages are not especially adapted to this sort of mechanization, it is true. It is strange that the inventors of universal languages have not seized upon the idea of producing one which better fitted the technique for transmitting and recording speech. Mechanization may yet force the issue, especially in the scientific field; whereupon scientific jargon would become still less intelligible to the layman.",{"_31":11250,"_33":11251},[],{"_35":160,"_37":11252,"_39":11030,"_41":11253,"_66":11254,"_68":11255,"_70":69},"vyT4Qh7J",{},[],"One can now picture a future investigator in his laboratory. His hands are free, and he is not anchored. As he moves about and observes, he photographs and comments. Time is automatically recorded to tie the two records together. If he goes into the field, he may be connected by radio to his recorder. As he ponders over his notes in the evening, he again talks his comments into the record. His typed record, as well as his photographs, may both be in miniature, so that he projects them for examination.",{"_31":11257,"_33":11258},[],{"_35":160,"_37":11259,"_39":11030,"_41":11260,"_66":11261,"_68":11262,"_70":69},"DjqvcW_2",{},[],"Much needs to occur, however, between the collection of data and observations, the extraction of parallel material from the existing record, and the final insertion of new material into the general body of the common record. For mature thought there is no mechanical substitute. But creative thought and essentially repetitive thought are very different things. For the latter there are, and may be, powerful mechanical aids.",{"_31":11264,"_33":11265},[],{"_35":160,"_37":11266,"_39":11030,"_41":11267,"_66":11268,"_68":11269,"_70":69},"BQYHdvom",{},[],"Adding a column of figures is a repetitive thought process, and it was long ago properly relegated to the machine. True, the machine is sometimes controlled by a keyboard, and thought of a sort enters in reading the figures and poking the corresponding keys, but even this is avoidable. Machines have been made which will read typed figures by photocells and then depress the corresponding keys; these are combinations of photocells for scanning the type, electric circuits for sorting the consequent variations, and relay circuits for interpreting the result into the action of solenoids to pull the keys down.",{"_31":11271,"_33":11272},[],{"_35":160,"_37":11273,"_39":11030,"_41":11274,"_66":11275,"_68":11276,"_70":69},"wfxQINaa",{},[],"All this complication is needed because of the clumsy way in which we have learned to write figures. If we recorded them positionally, simply by the configuration of a set of dots on a card, the automatic reading mechanism would become comparatively simple. In fact if the dots are holes, we have the punched-card machine long ago produced by Hollorith for the purposes of the census, and now used throughout business. Some types of complex businesses could hardly operate without these machines.",{"_31":11278,"_33":11279},[],{"_35":160,"_37":11280,"_39":11030,"_41":11281,"_66":11282,"_68":11283,"_70":69},"3rsmlV1G",{},[],"Adding is only one operation. To perform arithmetical computation involves also subtraction, multiplication, and division, and in addition some method for temporary storage of results, removal from storage for further manipulation, and recording of final results by printing. Machines for these purposes are now of two types: keyboard machines for accounting and the like, manually controlled for the insertion of data, and usually automatically controlled as far as the sequence of operations is concerned; and punched-card machines in which separate operations are usually delegated to a series of machines, and the cards then transferred bodily from one to another. Both forms are very useful; but as far as complex computations are concerned, both are still in embryo.",{"_31":11285,"_33":11286},[],{"_35":160,"_37":11287,"_39":11030,"_41":11288,"_66":11289,"_68":11290,"_70":69},"HAKoL0UH",{},[],"Rapid electrical counting appeared soon after the physicists found it desirable to count cosmic rays. For their own purposes the physicists promptly constructed thermionic-tube equipment capable of counting electrical impulses at the rate of 100,000 a second. The advanced arithmetical machines of the future will be electrical in nature, and they will perform at 100 times present speeds, or more.",{"_31":11292,"_33":11293},[],{"_35":160,"_37":11294,"_39":11030,"_41":11295,"_66":11296,"_68":11297,"_70":69},"UxBKYabq",{},[],"Moreover, they will be far more versatile than present commercial machines, so that they may readily be adapted for a wide variety of operations. They will be controlled by a control card or film, they will select their own data and manipulate it in accordance with the instructions thus inserted, they will perform complex arithmetical computations at exceedingly high speeds, and they will record results in such form as to be readily available for distribution or for later further manipulation. Such machines will have enormous appetites. One of them will take instructions and data from a whole roomful of girls armed with simple key board punches, and will deliver sheets of computed results every few minutes. There will always be plenty of things to compute in the detailed affairs of millions of people doing complicated things.",{"_35":870,"_37":11299,"_39":11030,"_41":11300,"_66":11301,"_68":11302,"_70":69},"Caz1YMi1",{"_273":323},[],"3",{"_31":11304,"_33":11340},[11305,11312,11319,11326,11333],{"_31":11306,"_33":11307},[],{"_35":160,"_37":11308,"_39":11030,"_41":11309,"_66":11310,"_68":11311,"_70":69},"X0LPMZba",{},[],"The repetitive processes of thought are not confined however, to matters of arithmetic and statistics. In fact, every time one combines and records facts in accordance with established logical processes, the creative aspect of thinking is concerned only with the selection of the data and the process to be employed and the manipulation thereafter is repetitive in nature and hence a fit matter to be relegated to the machine. Not so much has been done along these lines, beyond the bounds of arithmetic, as might be done, primarily because of the economics of the situation. The needs of business and the extensive market obviously waiting, assured the advent of mass-produced arithmetical machines just as soon as production methods were sufficiently advanced.",{"_31":11313,"_33":11314},[],{"_35":160,"_37":11315,"_39":11030,"_41":11316,"_66":11317,"_68":11318,"_70":69},"2eSzLikN",{},[],"With machines for advanced analysis no such situation existed; for there was and is no extensive market; the users of advanced methods of manipulating data are a very small part of the population. There are, however, machines for solving differential equations—and functional and integral equations, for that matter. There are many special machines, such as the harmonic synthesizer which predicts the tides. There will be many more, appearing certainly first in the hands of the scientist and in small numbers.",{"_31":11320,"_33":11321},[],{"_35":160,"_37":11322,"_39":11030,"_41":11323,"_66":11324,"_68":11325,"_70":69},"YpDlMGqW",{},[],"If scientific reasoning were limited to the logical processes of arithmetic, we should not get far in our understanding of the physical world. One might as well attempt to grasp the game of poker entirely by the use of the mathematics of probability. The abacus, with its beads strung on parallel wires, led the Arabs to positional numeration and the concept of zero many centuries before the rest of the world; and it was a useful tool—so useful that it still exists.",{"_31":11327,"_33":11328},[],{"_35":160,"_37":11329,"_39":11030,"_41":11330,"_66":11331,"_68":11332,"_70":69},"BmIiNLll",{},[],"It is a far cry from the abacus to the modern keyboard accounting machine. It will be an equal step to the arithmetical machine of the future. But even this new machine will not take the scientist where he needs to go. Relief must be secured from laborious detailed manipulation of higher mathematics as well, if the users of it are to free their brains for something more than repetitive detailed transformations in accordance with established rules. A mathematician is not a man who can readily manipulate figures; often he cannot. He is not even a man who can readily perform the transformations of equations by the use of calculus. He is primarily an individual who is skilled in the use of symbolic logic on a high plane, and especially he is a man of intuitive judgment in the choice of the manipulative processes he employs.",{"_31":11334,"_33":11335},[],{"_35":160,"_37":11336,"_39":11030,"_41":11337,"_66":11338,"_68":11339,"_70":69},"Fo67osVh",{},[],"All else he should be able to turn over to his mechanism, just as confidently as he turns over the propelling of his car to the intricate mechanism under the hood. Only then will mathematics be practically effective in bringing the growing knowledge of atomistics to the useful solution of the advanced problems of chemistry, metallurgy, and biology. For this reason there still come more machines to handle advanced mathematics for the scientist. Some of them will be sufficiently bizarre to suit the most fastidious connoisseur of the present artifacts of civilization.",{"_35":870,"_37":11341,"_39":11030,"_41":11342,"_66":11343,"_68":11344,"_70":69},"WoW7Eg8x",{"_273":323},[],"4",{"_31":11346,"_33":11417},[11347,11354,11361,11368,11375,11382,11389,11396,11403,11410],{"_31":11348,"_33":11349},[],{"_35":160,"_37":11350,"_39":11030,"_41":11351,"_66":11352,"_68":11353,"_70":69},"dbVFL4fA",{},[],"The scientist, however, is not the only person who manipulates data and examines the world about him by the use of logical processes, although he sometimes preserves this appearance by adopting into the fold anyone who becomes logical, much in the manner in which a British labor leader is elevated to knighthood. Whenever logical processes of thought are employed—that is, whenever thought for a time runs along an accepted groove—there is an opportunity for the machine. Formal logic used to be a keen instrument in the hands of the teacher in his trying of students' souls. It is readily possible to construct a machine which will manipulate premises in accordance with formal logic, simply by the clever use of relay circuits. Put a set of premises into such a device and turn the crank, and it will readily pass out conclusion after conclusion, all in accordance with logical law, and with no more slips than would be expected of a keyboard adding machine.",{"_31":11355,"_33":11356},[],{"_35":160,"_37":11357,"_39":11030,"_41":11358,"_66":11359,"_68":11360,"_70":69},"qI7bXze9",{},[],"Logic can become enormously difficult, and it would undoubtedly be well to produce more assurance in its use. The machines for higher analysis have usually been equation solvers. Ideas are beginning to appear for equation transformers, which will rearrange the relationship expressed by an equation in accordance with strict and rather advanced logic. Progress is inhibited by the exceedingly crude way in which mathematicians express their relationships. They employ a symbolism which grew like Topsy and has little consistency; a strange fact in that most logical field.",{"_31":11362,"_33":11363},[],{"_35":160,"_37":11364,"_39":11030,"_41":11365,"_66":11366,"_68":11367,"_70":69},"2DeyUdzh",{},[],"A new symbolism, probably positional, must apparently precede the reduction of mathematical transformations to machine processes. Then, on beyond the strict logic of the mathematician, lies the application of logic in everyday affairs. We may some day click off arguments on a machine with the same assurance that we now enter sales on a cash register. But the machine of logic will not look like a cash register, even of the streamlined model.",{"_31":11369,"_33":11370},[],{"_35":160,"_37":11371,"_39":11030,"_41":11372,"_66":11373,"_68":11374,"_70":69},"KBnJ0-B0",{},[],"So much for the manipulation of ideas and their insertion into the record. Thus far we seem to be worse off than before—for we can enormously extend the record; yet even in its present bulk we can hardly consult it. This is a much larger matter than merely the extraction of data for the purposes of scientific research; it involves the entire process by which man profits by his inheritance of acquired knowledge. The prime action of use is selection, and here we are halting indeed. There may be millions of fine thoughts, and the account of the experience on which they are based, all encased within stone walls of acceptable architectural form; but if the scholar can get at only one a week by diligent search, his syntheses are not likely to keep up with the current scene.",{"_31":11376,"_33":11377},[],{"_35":160,"_37":11378,"_39":11030,"_41":11379,"_66":11380,"_68":11381,"_70":69},"MYDxRxw5",{},[],"Selection, in this broad sense, is a stone adze in the hands of a cabinetmaker. Yet, in a narrow sense and in other areas, something has already been done mechanically on selection. The personnel officer of a factory drops a stack of a few thousand employee cards into a selecting machine, sets a code in accordance with an established convention, and produces in a short time a list of all employees who live in Trenton and know Spanish. Even such devices are much too slow when it comes, for example, to matching a set of fingerprints with one of five million on file. Selection devices of this sort will soon be speeded up from their present rate of reviewing data at a few hundred a minute. By the use of photocells and microfilm they will survey items at the rate of a thousand a second, and will print out duplicates of those selected.",{"_31":11383,"_33":11384},[],{"_35":160,"_37":11385,"_39":11030,"_41":11386,"_66":11387,"_68":11388,"_70":69},"7JIxh6TR",{},[],"This process, however, is simple selection: it proceeds by examining in turn every one of a large set of items, and by picking out those which have certain specified characteristics. There is another form of selection best illustrated by the automatic telephone exchange. You dial a number and the machine selects and connects just one of a million possible stations. It does not run over them all. It pays attention only to a class given by a first digit, then only to a subclass of this given by the second digit, and so on; and thus proceeds rapidly and almost unerringly to the selected station. It requires a few seconds to make the selection, although the process could be speeded up if increased speed were economically warranted. If necessary, it could be made extremely fast by substituting thermionic-tube switching for mechanical switching, so that the full selection could be made in one one-hundredth of a second. No one would wish to spend the money necessary to make this change in the telephone system, but the general idea is applicable elsewhere.",{"_31":11390,"_33":11391},[],{"_35":160,"_37":11392,"_39":11030,"_41":11393,"_66":11394,"_68":11395,"_70":69},"HSwtph6E",{},[],"Take the prosaic problem of the great department store. Every time a charge sale is made, there are a number of things to be done. The inventory needs to be revised, the salesman needs to be given credit for the sale, the general accounts need an entry, and, most important, the customer needs to be charged. A central records device has been developed in which much of this work is done conveniently. The salesman places on a stand the customer's identification card, his own card, and the card taken from the article sold—all punched cards. When he pulls a lever, contacts are made through the holes, machinery at a central point makes the necessary computations and entries, and the proper receipt is printed for the salesman to pass to the customer.",{"_31":11397,"_33":11398},[],{"_35":160,"_37":11399,"_39":11030,"_41":11400,"_66":11401,"_68":11402,"_70":69},"rDkc-rpW",{},[],"But there may be ten thousand charge customers doing business with the store, and before the full operation can be completed someone has to select the right card and insert it at the central office. Now rapid selection can slide just the proper card into position in an instant or two, and return it afterward. Another difficulty occurs, however. Someone must read a total on the card, so that the machine can add its computed item to it. Conceivably the cards might be of the dry photography type I have described. Existing totals could then be read by photocell, and the new total entered by an electron beam.",{"_31":11404,"_33":11405},[],{"_35":160,"_37":11406,"_39":11030,"_41":11407,"_66":11408,"_68":11409,"_70":69},"VnHx8GEY",{},[],"The cards may be in miniature, so that they occupy little space. They must move quickly. They need not be transferred far, but merely into position so that the photocell and recorder can operate on them. Positional dots can enter the data. At the end of the month a machine can readily be made to read these and to print an ordinary bill. With tube selection, in which no mechanical parts are involved in the switches, little time need be occupied in bringing the correct card into use—a second should suffice for the entire operation. The whole record on the card may be made by magnetic dots on a steel sheet if desired, instead of dots to be observed optically, following the scheme by which Poulsen long ago put speech on a magnetic wire. This method has the advantage of simplicity and ease of erasure. By using photography, however one can arrange to project the record in enlarged form and at a distance by using the process common in television equipment.",{"_31":11411,"_33":11412},[],{"_35":160,"_37":11413,"_39":11030,"_41":11414,"_66":11415,"_68":11416,"_70":69},"Bl9S1vY0",{},[],"One can consider rapid selection of this form, and distant projection for other purposes. To be able to key one sheet of a million before an operator in a second or two, with the possibility of then adding notes thereto, is suggestive in many ways. It might even be of use in libraries, but that is another story. At any rate, there are now some interesting combinations possible. One might, for example, speak to a microphone, in the manner described in connection with the speech controlled typewriter, and thus make his selections. It would certainly beat the usual file clerk.",{"_35":870,"_37":11418,"_39":11030,"_41":11419,"_66":11420,"_68":11421,"_70":69},"823Fb4_N",{"_273":323},[],"5",{"_31":11423,"_33":11487},[11424,11431,11438,11445,11452,11459,11466,11473,11480],{"_31":11425,"_33":11426},[],{"_35":160,"_37":11427,"_39":11030,"_41":11428,"_66":11429,"_68":11430,"_70":69},"-UV4qKcD",{},[],"The real heart of the matter of selection, however, goes deeper than a lag in the adoption of mechanisms by libraries, or a lack of development of devices for their use. Our ineptitude in getting at the record is largely caused by the artificiality of systems of indexing. When data of any sort are placed in storage, they are filed alphabetically or numerically, and information is found (when it is) by tracing it down from subclass to subclass. It can be in only one place, unless duplicates are used; one has to have rules as to which path will locate it, and the rules are cumbersome. Having found one item, moreover, one has to emerge from the system and re-enter on a new path.",{"_31":11432,"_33":11433},[],{"_35":160,"_37":11434,"_39":11030,"_41":11435,"_66":11436,"_68":11437,"_70":69},"BYXDVRVK",{},[],"The human mind does not work that way. It operates by association. With one item in its grasp, it snaps instantly to the next that is suggested by the association of thoughts, in accordance with some intricate web of trails carried by the cells of the brain. It has other characteristics, of course; trails that are not frequently followed are prone to fade, items are not fully permanent, memory is transitory. Yet the speed of action, the intricacy of trails, the detail of mental pictures, is awe-inspiring beyond all else in nature.",{"_31":11439,"_33":11440},[],{"_35":160,"_37":11441,"_39":11030,"_41":11442,"_66":11443,"_68":11444,"_70":69},"cwjOO8BP",{},[],"Man cannot hope fully to duplicate this mental process artificially, but he certainly ought to be able to learn from it. In minor ways he may even improve, for his records have relative permanency. The first idea, however, to be drawn from the analogy concerns selection. Selection by association, rather than indexing, may yet be mechanized. One cannot hope thus to equal the speed and flexibility with which the mind follows an associative trail, but it should be possible to beat the mind decisively in regard to the permanence and clarity of the items resurrected from storage.",{"_31":11446,"_33":11447},[],{"_35":160,"_37":11448,"_39":11030,"_41":11449,"_66":11450,"_68":11451,"_70":69},"AqGRgRAh",{},[],"Consider a future device for individual use, which is a sort of mechanized private file and library. It needs a name, and, to coin one at random, “memex” will do. A memex is a device in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility. It is an enlarged intimate supplement to his memory.",{"_31":11453,"_33":11454},[],{"_35":160,"_37":11455,"_39":11030,"_41":11456,"_66":11457,"_68":11458,"_70":69},"TfWCAxXp",{},[],"It consists of a desk, and while it can presumably be operated from a distance, it is primarily the piece of furniture at which he works. On the top are slanting translucent screens, on which material can be projected for convenient reading. There is a keyboard, and sets of buttons and levers. Otherwise it looks like an ordinary desk.",{"_31":11460,"_33":11461},[],{"_35":160,"_37":11462,"_39":11030,"_41":11463,"_66":11464,"_68":11465,"_70":69},"Ji-nrzmR",{},[],"In one end is the stored material. The matter of bulk is well taken care of by improved microfilm. Only a small part of the interior of the memex is devoted to storage, the rest to mechanism. Yet if the user inserted 5000 pages of material a day it would take him hundreds of years to fill the repository, so he can be profligate and enter material freely.",{"_31":11467,"_33":11468},[],{"_35":160,"_37":11469,"_39":11030,"_41":11470,"_66":11471,"_68":11472,"_70":69},"jYxXQch-",{},[],"Most of the memex contents are purchased on microfilm ready for insertion. Books of all sorts, pictures, current periodicals, newspapers, are thus obtained and dropped into place. Business correspondence takes the same path. And there is provision for direct entry. On the top of the memex is a transparent platen. On this are placed longhand notes, photographs, memoranda, all sorts of things. When one is in place, the depression of a lever causes it to be photographed onto the next blank space in a section of the memex film, dry photography being employed.",{"_31":11474,"_33":11475},[],{"_35":160,"_37":11476,"_39":11030,"_41":11477,"_66":11478,"_68":11479,"_70":69},"3lraYLjj",{},[],"There is, of course, provision for consultation of the record by the usual scheme of indexing. If the user wishes to consult a certain book, he taps its code on the keyboard, and the title page of the book promptly appears before him, projected onto one of his viewing positions. Frequently-used codes are mnemonic, so that he seldom consults his code book; but when he does, a single tap of a key projects it for his use. Moreover, he has supplemental levers. On deflecting one of these levers to the right he runs through the book before him, each page in turn being projected at a speed which just allows a recognizing glance at each. If he deflects it further to the right, he steps through the book 10 pages at a time; still further at 100 pages at a time. Deflection to the left gives him the same control backwards.",{"_31":11481,"_33":11482},[],{"_35":160,"_37":11483,"_39":11030,"_41":11484,"_66":11485,"_68":11486,"_70":69},"EN57UWfJ",{},[],"A special button transfers him immediately to the first page of the index. Any given book of his library can thus be called up and consulted with far greater facility than if it were taken from a shelf. As he has several projection positions, he can leave one item in position while he calls up another. He can add marginal notes and comments, taking advantage of one possible type of dry photography, and it could even be arranged so that he can do this by a stylus scheme, such as is now employed in the telautograph seen in railroad waiting rooms, just as though he had the physical page before him.",{"_35":870,"_37":11488,"_39":11030,"_41":11489,"_66":11490,"_68":11491,"_70":69},"hE72EiW7",{"_273":323},[],"6",{"_31":11493,"_33":11529},[11494,11501,11508,11515,11522],{"_31":11495,"_33":11496},[],{"_35":160,"_37":11497,"_39":11030,"_41":11498,"_66":11499,"_68":11500,"_70":69},"TlXiaXp1",{},[],"All this is conventional, except for the projection forward of present-day mechanisms and gadgetry. It affords an immediate step, however, to associative indexing, the basic idea of which is a provision whereby any item may be caused at will to select immediately and automatically another. This is the essential feature of the memex. The process of tying two items together is the important thing.",{"_31":11502,"_33":11503},[],{"_35":160,"_37":11504,"_39":11030,"_41":11505,"_66":11506,"_68":11507,"_70":69},"h2eYi2q9",{},[],"When the user is building a trail, he names it, inserts the name in his code book, and taps it out on his keyboard. Before him are the two items to be joined, projected onto adjacent viewing positions. At the bottom of each there are a number of blank code spaces, and a pointer is set to indicate one of these on each item. The user taps a single key, and the items are permanently joined. In each code space appears the code word. Out of view, but also in the code space, is inserted a set of dots for photocell viewing; and on each item these dots by their positions designate the index number of the other item.",{"_31":11509,"_33":11510},[],{"_35":160,"_37":11511,"_39":11030,"_41":11512,"_66":11513,"_68":11514,"_70":69},"rkpILk1-",{},[],"Thereafter, at any time, when one of these items is in view, the other can be instantly recalled merely by tapping a button below the corresponding code space. Moreover, when numerous items have been thus joined together to form a trail, they can be reviewed in turn, rapidly or slowly, by deflecting a lever like that used for turning the pages of a book. It is exactly as though the physical items had been gathered together from widely separated sources and bound together to form a new book. It is more than this, for any item can be joined into numerous trails.",{"_31":11516,"_33":11517},[],{"_35":160,"_37":11518,"_39":11030,"_41":11519,"_66":11520,"_68":11521,"_70":69},"K-wqZnlN",{},[],"The owner of the memex, let us say, is interested in the origin and properties of the bow and arrow. Specifically he is studying why the short Turkish bow was apparently superior to the English long bow in the skirmishes of the Crusades. He has dozens of possibly pertinent books and articles in his memex. First he runs through an encyclopedia, finds an interesting but sketchy article, leaves it projected. Next, in a history, he finds another pertinent item, and ties the two together. Thus he goes, building a trail of many items. Occasionally he inserts a comment of his own, either linking it into the main trail or joining it by a side trail to a particular item. When it becomes evident that the elastic properties of available materials had a great deal to do with the bow, he branches off on a side trail which takes him through textbooks on elasticity and tables of physical constants. He inserts a page of longhand analysis of his own. Thus he builds a trail of his interest through the maze of materials available to him.",{"_31":11523,"_33":11524},[],{"_35":160,"_37":11525,"_39":11030,"_41":11526,"_66":11527,"_68":11528,"_70":69},"DAwmGiOq",{},[],"And his trails do not fade. Several years later, his talk with a friend turns to the queer ways in which a people resist innovations, even of vital interest. He has an example, in the fact that the outraged Europeans still failed to adopt the Turkish bow. In fact he has a trail on it. A touch brings up the code book. Tapping a few keys projects the head of the trail. A lever runs through it at will, stopping at interesting items, going off on side excursions. It is an interesting trail, pertinent to the discussion. So he sets a reproducer in action, photographs the whole trail out, and passes it to his friend for insertion in his own memex, there to be linked into the more general trail.",{"_35":870,"_37":11530,"_39":11030,"_41":11531,"_66":11532,"_68":11533,"_70":69},"p1OJYYyQ",{"_273":323},[],"7",{"_31":11535,"_33":11606},[11536,11543,11550,11557,11564,11571,11578,11585,11592,11599],{"_31":11537,"_33":11538},[],{"_35":160,"_37":11539,"_39":11030,"_41":11540,"_66":11541,"_68":11542,"_70":69},"aJ5f5jF5",{},[],"Wholly new forms of encyclopedias will appear, ready made with a mesh of associative trails running through them, ready to be dropped into the memex and there amplified. The lawyer has at his touch the associated opinions and decisions of his whole experience, and of the experience of friends and authorities. The patent attorney has on call the millions of issued patents, with familiar trails to every point of his client’s interest. The physician, puzzled by a patient’s reactions, strikes the trail established in studying an earlier similar case, and runs rapidly through analogous case histories, with side references to the classics for the pertinent anatomy and histology. The chemist, struggling with the synthesis of an organic compound, has all the chemical literature before him in his laboratory, with trails following the analogies of compounds, and side trails to their physical and chemical behavior.",{"_31":11544,"_33":11545},[],{"_35":160,"_37":11546,"_39":11030,"_41":11547,"_66":11548,"_68":11549,"_70":69},"CrI3YWur",{},[],"The historian, with a vast chronological account of a people, parallels it with a skip trail which stops only on the salient items, and can follow at any time contemporary trails which lead him all over civilization at a particular epoch. There is a new profession of trail blazers, those who find delight in the task of establishing useful trails through the enormous mass of the common record. The inheritance from the master becomes, not only his additions to the world's record, but for his disciples the entire scaffolding by which they were erected.",{"_31":11551,"_33":11552},[],{"_35":160,"_37":11553,"_39":11030,"_41":11554,"_66":11555,"_68":11556,"_70":69},"U_9LaT7O",{},[],"Thus science may implement the ways in which man produces, stores, and consults the record of the race. It might be striking to outline the instrumentalities of the future more spectacularly, rather than to stick closely to methods and elements now known and undergoing rapid development, as has been done here. Technical difficulties of all sorts have been ignored, certainly, but also ignored are means as yet unknown which may come any day to accelerate technical progress as violently as did the advent of the thermionic tube. In order that the picture may not be too commonplace, by reason of sticking to present-day patterns, it may be well to mention one such possibility, not to prophesy but merely to suggest, for prophecy based on extension of the known has substance, while prophecy founded on the unknown is only a doubly involved guess.",{"_31":11558,"_33":11559},[],{"_35":160,"_37":11560,"_39":11030,"_41":11561,"_66":11562,"_68":11563,"_70":69},"rbCVLzDH",{},[],"All our steps in creating or absorbing material of the record proceed through one of the senses—the tactile when we touch keys, the oral when we speak or listen, the visual when we read. Is it not possible that some day the path may be established more directly?",{"_31":11565,"_33":11566},[],{"_35":160,"_37":11567,"_39":11030,"_41":11568,"_66":11569,"_68":11570,"_70":69},"tUjyp4qQ",{},[],"We know that when the eye sees, all the consequent information is transmitted to the brain by means of electrical vibrations in the channel of the optic nerve. This is an exact analogy with the electrical vibrations which occur in the cable of a television set: they convey the picture from the photocells which see it to the radio transmitter from which it is broadcast. We know further that if we can approach that cable with the proper instruments, we do not need to touch it; we can pick up those vibrations by electrical induction and thus discover and reproduce the scene which is being transmitted, just as a telephone wire may be tapped for its message.",{"_31":11572,"_33":11573},[],{"_35":160,"_37":11574,"_39":11030,"_41":11575,"_66":11576,"_68":11577,"_70":69},"tRsbCa9_",{},[],"The impulses which flow in the arm nerves of a typist convey to her fingers the translated information which reaches her eye or ear, in order that the fingers may be caused to strike the proper keys. Might not these currents be intercepted, either in the original form in which information is conveyed to the brain, or in the marvelously metamorphosed form in which they then proceed to the hand?",{"_31":11579,"_33":11580},[],{"_35":160,"_37":11581,"_39":11030,"_41":11582,"_66":11583,"_68":11584,"_70":69},"-RUSQJGe",{},[],"By bone conduction we already introduce sounds: into the nerve channels of the deaf in order that they may hear. Is it not possible that we may learn to introduce them without the present cumbersomeness of first transforming electrical vibrations to mechanical ones, which the human mechanism promptly transforms back to the electrical form? With a couple of electrodes on the skull the encephalograph now produces pen-and-ink traces which bear some relation to the electrical phenomena going on in the brain itself. True, the record is unintelligible, except as it points out certain gross misfunctioning of the cerebral mechanism; but who would now place bounds on where such a thing may lead?",{"_31":11586,"_33":11587},[],{"_35":160,"_37":11588,"_39":11030,"_41":11589,"_66":11590,"_68":11591,"_70":69},"DOt3yVEX",{},[],"In the outside world, all forms of intelligence whether of sound or sight, have been reduced to the form of varying currents in an electric circuit in order that they may be transmitted. Inside the human frame exactly the same sort of process occurs. Must we always transform to mechanical movements in order to proceed from one electrical phenomenon to another? It is a suggestive thought, but it hardly warrants prediction without losing touch with reality and immediateness.",{"_31":11593,"_33":11594},[],{"_35":160,"_37":11595,"_39":11030,"_41":11596,"_66":11597,"_68":11598,"_70":69},"O9yaYqlH",{},[],"Presumably man’s spirit should be elevated if he can better review his shady past and analyze more completely and objectively his present problems. He has built a civilization so complex that he needs to mechanize his records more fully if he is to push his experiment to its logical conclusion and not merely become bogged down part way there by overtaxing his limited memory. His excursions may be more enjoyable if he can reacquire the privilege of forgetting the manifold things he does not need to have immediately at hand, with some assurance that he can find them again if they prove important.",{"_31":11600,"_33":11601},[],{"_35":160,"_37":11602,"_39":11030,"_41":11603,"_66":11604,"_68":11605,"_70":69},"xlkEDzl2",{},[],"The applications of science have built man a well-supplied house, and are teaching him to live healthily therein. They have enabled him to throw masses of people against one another with cruel weapons. They may yet allow him truly to encompass the great record and to grow in the wisdom of race experience. He may perish in conflict before he learns to wield that record for his true good. Yet, in the application of science to the needs and desires of man, it would seem to be a singularly unfortunate stage at which to terminate the process, or to lose hope as to the outcome.",{"_35":870,"_37":11607,"_39":11030,"_41":11608,"_66":11609,"_68":11610,"_70":69},"08ZdhY57",{"_273":323},[],"8",[279],"/records/as-we-may-think","2025-04-02T15:47:27.962Z",{"_82":736,"_285":737,"_738":62},{},{"_37":715,"_95":53,"_54":11617,"_71":718,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,717],1772031973258,[149,715,718],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/as-we-may-think\",\"bafy2bzacec3kkhk7fwcoj2r3igjlqws2osakiwpnxyimlpsnklxrxwtyn6bpu\"]",{"_110":11622,"_147":12379,"_150":12380},{"_112":11623,"_131":132,"_133":12378,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":11624,"_37":12376},{"_28":11625,"_71":744,"_72":53,"_73":12372,"_54":12373,"_76":751,"_78":751,"_80":12374,"_84":12375,"_86":744,"_88":89},[11626,11637,11648,11657,11668,11694,11732,11764,11825,11916,12061,12129,12157,12185,12206,12226],{"_31":11627,"_33":11628},[],{"_35":160,"_37":11629,"_39":744,"_41":11630,"_66":11631,"_68":11636,"_70":69},"XhasNcRw",{},[11632],{"_35":166,"_167":11633,"_169":11634,"_41":11635,"_70":69},[137,7309,987,1000],[6448,1573,2416,6475],{},"Andrew M. Fountain, Wendy Hall, Ian Heath, and Hugh C. Davis",{"_31":11638,"_33":11639},[],{"_35":160,"_37":11640,"_39":744,"_41":11641,"_66":11642,"_68":11647,"_70":69},"uhPy138g",{},[11643],{"_35":919,"_167":11644,"_169":11645,"_41":11646,"_70":69},[137],[3409],{},"Department of Electronics and Computer Science University of Southampton Southampton SO95NH",{"_31":11649,"_33":11650},[],{"_35":8525,"_37":11651,"_39":744,"_41":11652,"_66":11655,"_68":69,"_70":11656},"_lUdRhiX",{"_8528":11653,"_82":11654},582465,"298-311_Fountain.pdf",[],"ipfs://bafybeiaajxfk7wgbxs7ax2wikm32bz7h4filzpiun5wbxueydhioosfdkm",{"_31":11658,"_33":11659},[],{"_35":160,"_37":11660,"_39":744,"_41":11661,"_66":11662,"_68":11667,"_70":69},"kisyDkpB",{},[11663],{"_35":166,"_167":11664,"_169":11665,"_41":11666,"_70":69},[137],[240],{},"ABSTRACT: There are currently a number of commercially available hypertext and hypermedia systems, of varying levels of sophistication and usability, but there are still many problems to be resolved in the design of such systems. In this paper, we itemise some of the major problems that we have identified as possibly causing a barrier to the growth and development of hypermedia applications outside the research community. A model of an open hypermedia architecture with dynamic linking features is proposed that moves some way to resolving these problems, and the first implementation of the system, Microcosm, is presented and discussed.",{"_31":11669,"_33":11670},[],{"_35":160,"_37":11671,"_39":744,"_41":11672,"_66":11673,"_68":11693,"_70":69},"o_PfuGMM",{},[11674,11678,11683,11688],{"_35":166,"_167":11675,"_169":11676,"_41":11677,"_70":69},[137],[240],{},{"_35":204,"_167":11679,"_169":11680,"_41":11681,"_70":11682},[6982],[7309],{},"hm://d/P8AJ4RvURPbDMQKyTsgWCo?v=bafy2bzacebjgt6zf7xm4uxy6e7aq6jnqme44zrcm57ukhapcz2f5dw3szgydy",{"_35":204,"_167":11684,"_169":11685,"_41":11686,"_70":11687},[1011],[3476],{},"hm://d/5yKBJKR5baKz6ZL5LumwPX?v=bafy2bzacebjhoib5lu33ljxcqj3f222j6jj5ujzx24btgkhoxioditxljaclc",{"_35":204,"_167":11689,"_169":11690,"_41":11691,"_70":11692},[2261],[9489],{},"hm://d/EgtvG7xCvqmdaKMDCsCSy8?v=bafy2bzaceakrdbigvs2qbh32w7hwi3c6hbgv6el3umq5jek7aub4c2g6ynoao","KEYWORDS: #hypertext, #multimedia, #dynamic linking",{"_31":11695,"_33":11727},[11696,11703,11720],{"_31":11697,"_33":11698},[],{"_35":160,"_37":11699,"_39":744,"_41":11700,"_66":11701,"_68":11702,"_70":69},"NnRF5d0l",{},[],"The terms hypertext and hypermedia are now so well known that definitions are unnecessary. Advances in computer power and performance have permitted the visionary concepts put forward by Bush [1945], Engelbart [1963] and Nelson [1967] to become a practical reality and we are now in a position to explore the implications, both positive and negative, of using hypertext systems for the management of information. The need for us to be able to control and utilise the phenomenal amounts of information that will be available to us through advances in technology, is the driving force behind the rapid pace of developments in hypertext and hypermedia systems. Much of the textual information that is available in the world today is stored or originally created in electronic format can be revised, edited and distributed easily as text files in a computer system. When we add to this the potential afforded by developments in optical disc technology for the storage of vast amounts of information from different media, we see the dawning of a new age of information processing.",{"_31":11704,"_33":11705},[],{"_35":160,"_37":11706,"_39":744,"_41":11707,"_66":11708,"_68":11719,"_70":69},"9rQ7cSUm",{},[11709],{"_35":919,"_167":11710,"_169":11714,"_41":11718,"_70":69},[956,11711,11712,11713],672,699,726,[6051,11715,11716,11717],678,705,732,{},"Traditional ways of presenting and distributing information in a linear fashion are no longer sufficient, and conventional database technology does not permit the wide range of functions required to fully exploit the potential of the new multimedia information systems. Neither of these strategies will become redundant but new systems must be developed that combine support for structured text, the handling of large volumes of data, the ability to mix media, and the freedom for the reader to switch seamlessly between the mixed media documents in the system [Rahtz et al. 1989a]. Hypertext and hypermedia techniques seem to offer much potential in this context ([Rahtz et al. 1989], [Yankelovich et al. 1988], [Shneiderman et al. 1989), but whilst providing solutions to many information processing problems, they naturally give rise to further sets of usability problems that have yet to be resolved ([Halasz 1988], [Nielsen 1990a]).",{"_31":11721,"_33":11722},[],{"_35":160,"_37":11723,"_39":744,"_41":11724,"_66":11725,"_68":11726,"_70":69},"pF2EWBai",{},[],"The use of hypertext and hypermedia systems is still largely confined to the research community. This is partly because of the limitations of commercially available systems and partly because of the tremendous effort required to create and maintain a hypertext system. These issues are compounded by the fact that currently available hypertext packages are basically closed systems, so that if material is created in one system it is very difficult to integrate it with material created in another system. We believe that this is a major barrier to the growth and development of hypertext and hypermedia applications outside the research community. This paper describes the design and implementation of a dynamic model of hypermedia that moves some way towards resolving these problems.",{"_35":870,"_37":11728,"_39":744,"_41":11729,"_66":11730,"_68":11731,"_70":69},"Jow66E4S",{"_273":323},[],"1 Introduction",{"_31":11733,"_33":11759},[11734,11741,11748],{"_31":11735,"_33":11736},[],{"_35":160,"_37":11737,"_39":744,"_41":11738,"_66":11739,"_68":11740,"_70":69},"Vu5aXi7E",{},[],"Nielsen's new book [Nielsen 1990b] gives a very full account of the nature of hypertext and hypermedia and describes the major systems that are currendy available. The two most widely used, certainly in the U.K., are Apple's HyperCard and OWL's Guide. It is a debatable point whether HyperCard can actually be described as a hypertext system. Its strength is in its rapid prototyping capabilities and it can certainly be used to simulate a hypertext environment through the means of its scripting language, HyperTalk. On the other hand, Guide developed from a research base at the University of Kent [Brown 1986], and was designed as a tool for reading documents on a computer. Guide has many well-defined and well-designed hypertext features which make it very easy to use. Version 2 of Guide had only limited extensibility but version 3, which has recently been released, incorporates a full scripting language.",{"_31":11742,"_33":11743},[],{"_35":160,"_37":11744,"_39":744,"_41":11745,"_66":11746,"_68":11747,"_70":69},"D7YX0WcL",{},[],"Both Guide and HyperCard have become successful commercially because they are easy to use and are readily available on the most widely used personal computer workstations, namely the IBM pc (or compatibles) and the Apple Macintosh. HyperCard is of course only available for the Macintosh range of computers but Apple's marketing ploy of giving a copy of HyperCard away free with every Macintosh has served to make HyperCard phenomenally successful as an application development environment. It is also possible to extend both Guide and HyperCard to incorporate multimedia information (such as image, sound and video) so that they can be classified as hypermedia systems. However, neither system provides a means for cataloguing or manipulating information about links independently from the documents in which they are activated. This means it is very difficult to provide summary information about links for maintaining, updating and enhancing the system, or to provide graphical browsing facilities and other sophisticated navigation tools. Guide overcomes navigation problems by controlling the types of buttons that the author can use and by emphasising the use of 'replacement' buttons in a scrolling text. However, HyperCard encourages a 'goto' approach to the creation of button and links and its very flexibility can be its downfall as far as controlling the development of the application is concerned.",{"_31":11749,"_33":11750},[],{"_35":160,"_37":11751,"_39":744,"_41":11752,"_66":11753,"_68":11758,"_70":69},"iSJK1YVZ",{},[11754],{"_35":919,"_167":11755,"_169":11756,"_41":11757,"_70":69},[1508],[185],{},"Other well-known hypertext systems, such as Intermedia [Yankelovich et al. 1988], Notecards [Halasz 1988] and Hyperties [Shneiderman 1987], have also developed out of large research projects and contain many highly sophisticated and well-researched hypertext features and navigation tools. They all embody the concept of a database of nodes and links but with very different models of design. The Intermedia project at Brown University is probably the most well- known and most often referenced hypertext research project. It was designed for educational use at the university level and has been used to teach several courses in subjects such as biology and English literature. Hyperties is well-known as the system in which the hypertext version of the July'88 issue of the CACM was issued, and for the computer-based version of the book Hypertext Hands On [Shneiderman & Kearsley 1989]. It is available for the IBM pc and has been used extensively for museum applications [Shneiderman *et al. *1989]. Intermedia and Notecards both require high-powered Unix workstations and this may limit their use outside of the research environment in the immediate future.",{"_35":870,"_37":11760,"_39":744,"_41":11761,"_66":11762,"_68":11763,"_70":69},"uzofeeFl",{"_273":323},[],"2 Current Hypermedia Systems",{"_31":11765,"_33":11820},[11766,11773,11784,11795,11806,11813],{"_31":11767,"_33":11768},[],{"_35":160,"_37":11769,"_39":744,"_41":11770,"_66":11771,"_68":11772,"_70":69},"MduvnlBF",{},[],"We consider that there are four problems common to many current hypertext systems, which act as possible barriers to the creation, extension and integration of hypertext document systems.",{"_31":11774,"_33":11775},[],{"_35":160,"_37":11776,"_39":744,"_41":11777,"_66":11778,"_68":11783,"_70":69},"8M9w4xkw",{},[11779],{"_35":919,"_167":11780,"_169":11781,"_41":11782,"_70":69},[137],[3363],{},"Authoring effort required. The large effort required to insert links into documents is seen as one of the main limitations of hypertext systems. Documents are becoming available in computer readable form far faster than they can be converted to hypertext. The user of a hypertext system may often feel frustration that they are limited to the documents that have been painstakingly converted to run under their system.",{"_31":11785,"_33":11786},[],{"_35":160,"_37":11787,"_39":744,"_41":11788,"_66":11789,"_68":11794,"_70":69},"PVZuuQS9",{},[11790],{"_35":919,"_167":11791,"_169":11792,"_41":11793,"_70":69},[137],[3407],{},"Hypertext systems are closed. Hypertext systems are usually run as stand alone programs and will not communicate bi-directionally with other software packages. Often it is possible to add drivers to extend the system, but these connections are not usually bi-directional in the sense that external programs can access the hypertext linking mechanisms. It is seen as important to be able to integrate a hypertext system into the user's whole environment and this requires an open system. When multimedia documents are used, it is often necessary to add support for extra video/graphics formats. A system that has been designed to be open can provide for this sort of extensibility.",{"_31":11796,"_33":11797},[],{"_35":160,"_37":11798,"_39":744,"_41":11799,"_66":11800,"_68":11805,"_70":69},"scWgQgWd",{},[11801],{"_35":919,"_167":11802,"_169":11803,"_41":11804,"_70":69},[137],[3407],{},"Proprietary document formats. In general it is not possible to take documents produced in one system (e.g. Guide) and use them in another (e.g. Hypercard). Document formats are sometimes closely guarded secrets. This exacerbates the authoring problem above, and makes it difficult to write conversion programs from one format into another.",{"_31":11807,"_33":11808},[],{"_35":160,"_37":11809,"_39":744,"_41":11810,"_66":11811,"_68":11812,"_70":69},"mqBgd_hm",{},[],"*Problems with read-only media. *Many hypertext systems implement links by means of tags and pointers embedded in documents. With CD-ROMs and networked files it is not possible to freely add links into documents. Although hypertext CD-ROMs are available, the links are hard-coded into the documents and cannot be added to or changed on the medium itself. We believe that it is vital for the users of hypertext systems to be able to add their own links and annotations.",{"_31":11814,"_33":11815},[],{"_35":160,"_37":11816,"_39":744,"_41":11817,"_66":11818,"_68":11819,"_70":69},"FlPgRU7L",{},[],"Clearly, some hypertext systems partly solve these problems, for example Intermedia keeps link information separate from the documents themselves, but we have attempted to design a new system that solves them all by providing an open model for hypertext/hypermedia with dynamic linking capabilities. The first instantiation of this new system is called Microcosm.",{"_35":870,"_37":11821,"_39":744,"_41":11822,"_66":11823,"_68":11824,"_70":69},"3dMQtrbn",{"_273":323},[],"3 Problems with Current Systems",{"_31":11826,"_33":11911},[11827,11834,11841,11852,11863,11875,11882,11889,11896,11903],{"_31":11828,"_33":11829},[],{"_35":160,"_37":11830,"_39":744,"_41":11831,"_66":11832,"_68":11833,"_70":69},"Alh3AHFG",{},[],"Microcosm has been designed with a set of guiding principles. Each design decision was made by evaluating the alternatives against this set of principles:",{"_31":11835,"_33":11836},[],{"_35":160,"_37":11837,"_39":744,"_41":11838,"_66":11839,"_68":11840,"_70":69},"X8FnIu02",{},[],"*No ultimate distinction between author and user: *All users should be in a position to add linking information to the system. The task of having to structure knowledge by adding links can be an effective learning experience and does not belong only to the teacher domain.",{"_31":11842,"_33":11843},[],{"_35":160,"_37":11844,"_39":744,"_41":11845,"_66":11846,"_68":11851,"_70":69},"t6qtkOue",{},[11847],{"_35":919,"_167":11848,"_169":11849,"_41":11850,"_70":69},[137],[1539],{},"Loosely coupled system with a low level of interdependency: Microcosm is not just one program, it is a set of communicating tasks, open in structure. It should be possible to couple any other program into the system.",{"_31":11853,"_33":11854},[],{"_35":160,"_37":11855,"_39":744,"_41":11856,"_66":11857,"_68":11862,"_70":69},"2tJwvp4F",{},[11858],{"_35":919,"_167":11859,"_169":11860,"_41":11861,"_70":69},[137],[1783],{},"Modular to allow for slot-in experimental replacements. Microcosm is intended to be the workbench for a research environment. Every element, such as the linker, the document viewers, etc. must be replaceable. The system must be configurable and flexible so it may be used for investigating different ideas.",{"_31":11864,"_33":11865},[],{"_35":160,"_37":11866,"_39":744,"_41":11867,"_66":11868,"_68":11874,"_70":69},"CYcLBOs4",{},[11869],{"_35":919,"_167":11870,"_169":11871,"_41":11873,"_70":69},[137],[11872],38,{},"Separation of links from data objects: Information about relationships between documents is separated from the documents themselves, and is abstracted to a higher level. There are two worlds of information: the world of raw information: resource bases of text, graphics, video and sound; and the world of relationships and links between ideas, words, phrases, images and documents. Microcosm aims to keep these separate.",{"_31":11876,"_33":11877},[],{"_35":160,"_37":11878,"_39":744,"_41":11879,"_66":11880,"_68":11881,"_70":69},"PAni92Q3",{},[],"Document, Viewers",{"_31":11883,"_33":11884},[],{"_35":160,"_37":11885,"_39":744,"_41":11886,"_66":11887,"_68":11888,"_70":69},"G9JBMT0M",{},[],"External Windows Application",{"_31":11890,"_33":11891},[],{"_35":160,"_37":11892,"_39":744,"_41":11893,"_66":11894,"_68":11895,"_70":69},"e6oSI4sj",{},[],"External DOS - Application",{"_31":11897,"_33":11898},[],{"_35":160,"_37":11899,"_39":744,"_41":11900,"_66":11901,"_68":11902,"_70":69},"S2YqR81f",{},[],"Document Control System",{"_31":11904,"_33":11905},[],{"_35":1875,"_37":11906,"_39":744,"_41":11907,"_66":11908,"_68":11909,"_70":11910},"2Fl1gbfU",{},[],"Figure 1: Microcosm Tasks","ipfs://bafkreieuf6gimgzpw3p3txjofux4e6uf7uhjuj5a2o7hxsa4mgvyjufkha",{"_35":870,"_37":11912,"_39":744,"_41":11913,"_66":11914,"_68":11915,"_70":69},"nHRfE2hD",{"_273":323},[],"4 Principles",{"_31":11917,"_33":12056},[11918,11944,11984],{"_31":11919,"_33":11935},[11920],{"_31":11921,"_33":11922},[],{"_35":160,"_37":11923,"_39":744,"_41":11924,"_66":11925,"_68":11934,"_70":69},"zTvUzCuZ",{},[11926],{"_35":919,"_167":11927,"_169":11930,"_41":11933,"_70":69},[6475,11928,11929],242,876,[7128,11931,11932],258,897,{},"In a Microcosm session, at least two tasks are running. The Document Control System opens documents routes messages and supports links. Most of the time it is not visible to the user except as an icon at the bottom of the screen. One or more Document Viewers are used to display document on the screen. One viewer is running for each document visible. Different viewers are used for different types of document or medium. Currently there are viewers for text (plain ASCII), monochrome and colour bit-mapped graphics, vector graphics, animated graphics, CD sound, and still or moving video from a video disk. There may be a mix of viewers on the screen at the same time and the software imposes no limit in practice to the number running. Document viewers communicate by means of messages, and all messages are routed through the Document Control System. A third type of task, External Applications may also be running. These are applications which are not part of the Microcosm system but can be linked in by the Document Control System. For example, a spreadsheet can be used for graphing figures, or information can be extracted from a database, or from another hypertext system.",{"_35":870,"_37":11936,"_39":744,"_41":11937,"_66":11938,"_68":11943,"_70":69},"46jxSdky",{"_273":323},[11939],{"_35":919,"_167":11940,"_169":11941,"_41":11942,"_70":69},[137],[985],{},"5.1 Microcosm Tasks",{"_31":11945,"_33":11975},[11946,11960,11968],{"_31":11947,"_33":11948},[],{"_35":160,"_37":11949,"_39":744,"_41":11950,"_66":11951,"_68":11959,"_70":69},"Y8GjrY7D",{},[11952],{"_35":919,"_167":11953,"_169":11956,"_41":11958,"_70":69},[11954,11955],186,427,[6212,11957],446,{},"The basic mechanism of Microcosm is the message. It is used for following links, creating links, opening new documents and invoking programs. The message contains three essential parts: a selection which will typically be one or more words of text or an area of an image or graphic object selected by the user, an action which is to be performed on the selection, such as \"follow link\" or \"look this up in the dictionary\"; and context information which includes the name of the document containing the selection, its position in that document, the date, and the user's name.",{"_31":11961,"_33":11962},[],{"_35":1875,"_37":11963,"_39":744,"_41":11964,"_66":11965,"_68":11966,"_70":11967},"gKTGpRfz",{},[],"Figure 2: Message Format","ipfs://bafkreid44jpqak6czdm3wjmmrsgr3hrbauwmghcoeg44byvvas7wozrble",{"_31":11969,"_33":11970},[],{"_35":160,"_37":11971,"_39":744,"_41":11972,"_66":11973,"_68":11974,"_70":69},"lJ-rEo2a",{},[],"A message can be created in two ways. The simplest way is by the user highlighting a selection on the screen using a mouse, and then pulling down a menu of actions from a menu bar. Chosing an action will cause the message to be dispatched. The context information is provided by the document viewer. Messages are also created when buttons are pressed. Each document that has had buttons created for it has a button file associated with it. This button file contains a list of the locations of buttons within the document. A selection and an action are also stored for each button. A button then is merely a pre-defined selection bound to an action. It is a special case of the much more general message mechanism.",{"_35":870,"_37":11976,"_39":744,"_41":11977,"_66":11978,"_68":11983,"_70":69},"lZI8HeO-",{"_273":323},[11979],{"_35":919,"_167":11980,"_169":11981,"_41":11982,"_70":69},[137],[1011],{},"5.2 Microcosm Messages",{"_31":11985,"_33":12047},[11986,12001,12008,12015,12023,12031,12039],{"_31":11987,"_33":11988},[],{"_35":160,"_37":11989,"_39":744,"_41":11990,"_66":11991,"_68":12000,"_70":69},"Lyxt82fM",{},[11992],{"_35":919,"_167":11993,"_169":11996,"_41":11999,"_70":69},[1854,11994,11995],303,458,[11997,830,11998],241,469,{},"When the Document Control System receives a message it processes it according to the action. Each action has a task associated with it, and the task will be started up and send the required message. For example, if the action was create link then the message will be sent to the link creator. If it was search dictionary then the DOS dictionary application will be invoked with the message placed on the command line or in a data file as desired. The action follow link is the most common and so will be described in more detail.",{"_31":12002,"_33":12003},[],{"_35":160,"_37":12004,"_39":744,"_41":12005,"_66":12006,"_68":12007,"_70":69},"nZe1eheW",{},[],"Links are stored in a link database. This is a simple flat file system with one record per link. Each record associates a link message with a dispatch message. When the linker receives a follow link action, it attempts to match the rest of the message with a link message in the database. The way this match is performed is dependant on information entered at the time the links were created about how specific or general the link is. If a match is found, then the dispatch message is sent back to the Document Control System. It contains the name of the target document and offset into it where the link was directed. This information is used to start up a Document Viewer of the appropriate type, load the target document, and move to the specified location. In this instance, the user is not aware of the operation of the Document Control System at all. As far as they are concerned they have asked to follow a link and the new document has appeared in another window.",{"_31":12009,"_33":12010},[],{"_35":160,"_37":12011,"_39":744,"_41":12012,"_66":12013,"_68":12014,"_70":69},"prbInvgr",{},[],"Things are slightly more complicated if more than one link is available from a given selection. The user is then presented with a menu of links from which one or more may be chosen. Figures 3—6 illustrate the process of creating and following links",{"_31":12016,"_33":12017},[],{"_35":1875,"_37":12018,"_39":744,"_41":12019,"_66":12020,"_68":12021,"_70":12022},"mILPCyxW",{},[],"Figure 3: Screen shot of Microcosm showing a file relating to the Mountbatten archive from which the user has chosen to make a link on the phrase ","ipfs://bafkreidrqhxg775kmvh76nzrbuaiqdhhn5ju3ytnfxxe52z3lcvkgjiq4q",{"_31":12024,"_33":12025},[],{"_35":1875,"_37":12026,"_39":744,"_41":12027,"_66":12028,"_68":12029,"_70":12030},"ND8F-lHc",{},[],"Figure 4: The link database has three links for the word ","ipfs://bafybeifp562aogtgfq25rhm7dlsfkqj3y5yekxksdinpjkcoq53755quuy",{"_31":12032,"_33":12033},[],{"_35":1875,"_37":12034,"_39":744,"_41":12035,"_66":12036,"_68":12037,"_70":12038},"zuhH0vdX",{},[],"Figure 5: The biography text file appears in another window and the user chooses to complete the link made on the phrase ","ipfs://bafybeihc7k4xgcrecakcgypxqrbuussmsic3lsvlf35mpbgberoi3tdipq",{"_31":12040,"_33":12041},[],{"_35":1875,"_37":12042,"_39":744,"_41":12043,"_66":12044,"_68":12045,"_70":12046},"V7yFg_xS",{},[],"Figure 6: The link is made to apply from anywhere in any document. Thus a generic link has been created on the phrase ","ipfs://bafybeih5uylsxrfyges7ssdjmryvaiw3jldqin7mqjp2vgq5sqjgzojh4u",{"_35":870,"_37":12048,"_39":744,"_41":12049,"_66":12050,"_68":12055,"_70":69},"193SB84G",{"_273":323},[12051],{"_35":919,"_167":12052,"_169":12053,"_41":12054,"_70":69},[137],[1011],{},"5.3 Message Processing",{"_35":870,"_37":12057,"_39":744,"_41":12058,"_66":12059,"_68":12060,"_70":69},"Xtc9lzuN",{"_273":323},[],"5 Design",{"_31":12062,"_33":12124},[12063,12088,12106],{"_31":12064,"_33":12079},[12065],{"_31":12066,"_33":12067},[],{"_35":160,"_37":12068,"_39":744,"_41":12069,"_66":12070,"_68":12078,"_70":69},"6qxZHgpv",{},[12071],{"_35":919,"_167":12072,"_169":12075,"_41":12077,"_70":69},[12073,12074],140,1060,[6675,12076],1066,{},"Instead of storing the link information in with the documents, it is separated out into a knowledge base. This separation allows link to be generic, that is they are not applicable to only one document, but may be used with a whole class of documents. This greatly reduces the authoring effort required, since a new document can be brought into the system and immediately contain links. The Microcosm philosophy is that hypermedia links in themselves are a valuable store of knowledge. If this knowledge is bound too tightly to the documents, then it cannot be applied to new data. Instead it should be pushed away from the documents, into a world of generic knowledge. Microcosm aims to abstract the annotations, cross-references, and other knowledge and tools, so that when new documents are introduced, they immediately have links and cross references available. It should be possible to read a new paper on for example, microbiology, and merely to have to classify the subject of the paper to have a whole wealth of knowledge linked to the it. If the word amoeba had been linked to a videodisc clip of a moving amoeba, and the link had been specified as generic, then new document containing the word would automatically have the link. With the addition of simple filters, the information contained in the links can be applied to different areas of knowledge, being as generic or specific as wished.",{"_35":870,"_37":12080,"_39":744,"_41":12081,"_66":12082,"_68":12087,"_70":69},"6rRfAyOS",{"_273":323},[12083],{"_35":919,"_167":12084,"_169":12085,"_41":12086,"_70":69},[137],[7260],{},"6.1 Authoring effort required—generic links.",{"_31":12089,"_33":12097},[12090],{"_31":12091,"_33":12092},[],{"_35":160,"_37":12093,"_39":744,"_41":12094,"_66":12095,"_68":12096,"_70":69},"tOJKrVQC",{},[],"The separation of link information from documents has the benefit of allowing links to be made from read-only media such as CD-ROMs and remote file servers. This also simplifies links to and from media such as video and sound.",{"_35":870,"_37":12098,"_39":744,"_41":12099,"_66":12100,"_68":12105,"_70":69},"nvYKuqf6",{"_273":323},[12101],{"_35":919,"_167":12102,"_169":12103,"_41":12104,"_70":69},[137],[7309],{},"6.2 Read-only media.",{"_31":12107,"_33":12115},[12108],{"_31":12109,"_33":12110},[],{"_35":160,"_37":12111,"_39":744,"_41":12112,"_66":12113,"_68":12114,"_70":69},"xztLBOJI",{},[],"This is particularly important in a distributed hypertext, where it may be necessary to send out messages to remote machines (and slow to respond peripherals such as videodisc players) and then return control to the user while waiting for the remote responses, presumably while displaying some visual clue that they are still waiting for some response.",{"_35":870,"_37":12116,"_39":744,"_41":12117,"_66":12118,"_68":12123,"_70":69},"3XX1BZDj",{"_273":323},[12119],{"_35":919,"_167":12120,"_169":12121,"_41":12122,"_70":69},[137],[11872],{},"6.3 The possibilities for parallelism.",{"_35":870,"_37":12125,"_39":744,"_41":12126,"_66":12127,"_68":12128,"_70":69},"XEkQ2-d-",{"_273":323},[],"6 Implications",{"_31":12130,"_33":12152},[12131,12138,12145],{"_31":12132,"_33":12133},[],{"_35":160,"_37":12134,"_39":744,"_41":12135,"_66":12136,"_68":12137,"_70":69},"5TrbxzsG",{},[],"The first implementation of Microcosm was prototyped in Actor and then fully implemented in C and MS Windows version 3.0. It runs on IBM PCs (or compatibles) with a 286 processor or above. MS Windows provided us with the basic building blocks for Microcosm, namely the windows and icon interface, tools for creating pull-down menus and dialogue boxes as required, and multi tasking capability. It also provided a convenient message passing system, the Dynamic Data Exchange (DDE), which was used to handle interprocess communication in the Microcosm Document Control System.",{"_31":12139,"_33":12140},[],{"_35":160,"_37":12141,"_39":744,"_41":12142,"_66":12143,"_68":12144,"_70":69},"m7MgBeJ0",{},[],"The task of developing programs for MS Windows using the Software Developers Kit (SDK) can be very time consuming, especially to start with when there is a steep learning curve to be scaled. For this reason we conducted various experiments with the programming language ACTOR [Davis & Heath 1989] which is a single inheritance object oriented programming language similar to Smalltalk, but using MS Windows for its development environment, and producing MS Windows executable programs. While we found development in the ACTOR environment to be much faster, we found that the memory required was too great to allow it to run with other programs, and this prevented us developing the full loosely coupled communication process model in ACTOR. However, we were able to construct a restricted version of the Microcosm system using ACTOR in a relatively short period of time (about 3 weeks of part-time work by one person), and this turned out to be an ideal way of prototyping the user interface of the full system.",{"_31":12146,"_33":12147},[],{"_35":160,"_37":12148,"_39":744,"_41":12149,"_66":12150,"_68":12151,"_70":69},"rrGIx63U",{},[],"The first full implementation of Microcosm in MS Windows was ready for application development in January 1990. Our first application has been in the area of history and in particular in the development of an electronic version of the Mountbatten Archive. This archive is kept and maintained by the Hartley Library at the University of Southampton, and contains approximately 250,000 text documents, 50,000 photographs, 35 reels of cine film, and various audio and video tapes from the collection of the late Lord Mountbatten of Burma. The challenge is to make this archive available to historians in a way that permits explicit and implicit relationships between the different elements of the archive (text, photographs, film etc.) to be stored and analysed. Together with other colleagues at the University we have created a prototype of the electronic archive, taking documents and photographs from the period 1947-8, when Mountbatten was Viceroy of India. Currently, the text documents are stored as ASCII files on the hard-disc and the photographs are stored on a laser videodisc. Images from the latter are displayed in windows on the VGA screen of the computer workstation via a VideoLogic DVA-4000 board. This application provided the content of Figures i, and has allowed us to explore the potential of the various features that are built into Microcosm. A fuller report of this application and our work with the Department of History at Southampton is given in [Colson & Hall 1990].",{"_35":870,"_37":12153,"_39":744,"_41":12154,"_66":12155,"_68":12156,"_70":69},"WrY1b_Vv",{"_273":323},[],"7 Current State of Development",{"_31":12158,"_33":12180},[12159,12166,12173],{"_31":12160,"_33":12161},[],{"_35":160,"_37":12162,"_39":744,"_41":12163,"_66":12164,"_68":12165,"_70":69},"wIT2PWhV",{},[],"Navigation facilities within Microcosm are currently very limited. Users move around the system by following links, initiating database searches and manipulating the windows and icons in which the information appears. This is clearly unsatisfactory for the majority of users especially when the information space is very large (as in the Mountbatten application). An immediate priority is to explore how some of the 'standard' hypertext navigation features, such as contents and index lists, overview maps,and guided tours, can be applied and possibly extended in Microcosm, and if any new navigation tools are suggested by the Microcosm model. One of the main problems inherent in a loosely coupled system such as Microcosm is to let the user know what areas of the screen are active. In most hypertext systems the link anchor is specific, and so some visual clue is displayed to indicate where the anchor is, but in Microcosm, the generality of the linking mechanism makes such clues more difficult to create.",{"_31":12167,"_33":12168},[],{"_35":160,"_37":12169,"_39":744,"_41":12170,"_66":12171,"_68":12172,"_70":69},"n5dndQRb",{},[],"We conducted various experiments using the ACTOR version of Microcosm, and found that so long as a reasonably fast database is used to store the links, it is not unreasonable to search the entire database for links that are specific to the document at load time, and then to search the document file for the positions at which the visual clue should be inserted. However, inserting clues for links with a greater degree of generality is a problem. Clearly it is not reasonable to attempt to match every generic link in the database into the file, if the number of links is very large. Neither is it reasonable, if the file is very large, to attempt to match every possible text string in the file against the database. We found that the most acceptable solution to this problem was to allow the user to select an area of interest, and to select a menu option to match all possible strings in the selection against the database, and to display any matches found.",{"_31":12174,"_33":12175},[],{"_35":160,"_37":12176,"_39":744,"_41":12177,"_66":12178,"_68":12179,"_70":69},"iiHQO5wZ",{},[],"Another problem area in current hypertext systems that we plan to explore in Microcosm is version control and cooperative work. A number of solutions to this problem have been suggested in the hypertext literature [Akscyn 1988, Yankelovich et al 1985, Delise 1987], The next version of Microcosm will have a system of installable filters. It is intended to include a system for version control similar to Intermedia's webs, but which would allow for separate users by allowing a hierarchy of installed filters, so that for example, the main filter might add the links for a particular user.",{"_35":870,"_37":12181,"_39":744,"_41":12182,"_66":12183,"_68":12184,"_70":69},"SducKQrC",{"_273":323},[],"8 Research Directions",{"_31":12186,"_33":12201},[12187,12194],{"_31":12188,"_33":12189},[],{"_35":160,"_37":12190,"_39":744,"_41":12191,"_66":12192,"_68":12193,"_70":69},"_1hpi_4K",{},[],"One of the main barriers to progress in the field of hypertext is the effort required to convert linear text to hypertext. Although vast numbers of pages are available on line, few of them have been converted to hypertext, and even fewer were intentionally authored as such. Users may rapidly come to expect to find very large amounts of information available as hypertexts, so methods of converting linear texts are an area of current research. Most attempts to convert linear documents [Furuta et al. 1989, Rahtz et al. 1989] so far have concentrated on the use of the structure of the document to break the document into appropriately sized nodes, then on using adapted indexing and cross referencing tools to automate link production, in order to produce a framework hypertext, which will usually require further manual cross referencing and linking. Nielsen [1990b] states that links in hypertext systems are \"almost always anchored\" at their departure point. In Microcosm we have move away from this principle: the selection and action mechanism, which provides the generic linking capability within the system, gives us a different, and we believe very powerful, method for assisting the authoring effort. This has already been proven extremely effective in providing hypertext/hypermedia access to a large multimedia archive. A word or phrase has only to be designated a generic link once for this to apply across the whole set of documents in the system and any new documents that are brought into the system. This facility then applies directly to documents stored on read-only media without any extra processing of the documents.",{"_31":12195,"_33":12196},[],{"_35":160,"_37":12197,"_39":744,"_41":12198,"_66":12199,"_68":12200,"_70":69},"5kHIzSG8",{},[],"The main principles of Microcosm's design - its open nature, multi-tasking capabilities, bi-directional process communication and the separation of links into a separate database - have allowed us to create a very powerful and flexible hypermedia system. In Microcosm it is possible to run Guide, say, as a Windows application and thus read Guide documents exactly as they were authored, but at the same time to apply links created within the Microcosm environment to the Guide document using the selection/action mechanism of Microcosm. Links can launch database searches or activate videodisc access, so that if we bring a new document into the system, in whatever format, words or phrases in that document can be linked, for example, to a videodisc database that has been previously created within Microcosm, with no extra authoring effort. These facilities enable the user to fully integrate documents authored in other hypertext/hypermedia systems into their own hypermedia knowledge-base.",{"_35":870,"_37":12202,"_39":744,"_41":12203,"_66":12204,"_68":12205,"_70":69},"7tW-GVfj",{"_273":323},[],"9 Conclusions",{"_31":12207,"_33":12222},[12208,12215],{"_31":12209,"_33":12210},[],{"_35":160,"_37":12211,"_39":744,"_41":12212,"_66":12213,"_68":12214,"_70":69},"u4sJpcjH",{},[],"Representations of photographs from the Mountbatten archive appear by kind permission of Trustees of the Broadlands Archives Trust.",{"_31":12216,"_33":12217},[],{"_35":160,"_37":12218,"_39":744,"_41":12219,"_66":12220,"_68":12221,"_70":69},"XIjtP9JH",{},[],"We are extremely grateful to colleagues in the Department of History HiDES project, the Archives and Manuscripts Department of the Hartley Library, and the Department of Teaching Media for their invaluable support and assistance in the application of Microcosm to the Mountbatten Archive.Thanks are also due to colleagues in the Department of Electronics and Computer Science who contributed so much to the early discussions on the design of Microcosm.",{"_35":870,"_37":12223,"_39":744,"_41":12224,"_66":12225,"_68":3315,"_70":69},"ppbbmkQj",{"_273":323},[],{"_31":12227,"_33":12368},[12228,12235,12242,12249,12256,12263,12270,12277,12284,12291,12298,12305,12312,12319,12326,12333,12340,12347,12354,12361],{"_31":12229,"_33":12230},[],{"_35":160,"_37":12231,"_39":744,"_41":12232,"_66":12233,"_68":12234,"_70":69},"LS6JgZDR",{},[],"[Akscyn 1988] R. Akscyn, D.L. McCracken & E. Yoder, \"KMS: A Distributed Hypertext System for Managing Knowledge in Organizations\", Communcations of the ACM, Vol. 31, No. 7, 1988, pp 820-835.",{"_31":12236,"_33":12237},[],{"_35":160,"_37":12238,"_39":744,"_41":12239,"_66":12240,"_68":12241,"_70":69},"lZvbrDtL",{},[],"[Brown 1986] P.J. Brown, \"Interactive Documentation\", Software Practice and Experience, March 1986, pp 291-299.",{"_31":12243,"_33":12244},[],{"_35":160,"_37":12245,"_39":744,"_41":12246,"_66":12247,"_68":12248,"_70":69},"HgeIuk96",{},[],"[Bush 1945] V. BUSH, \"As We May Think\", Atlantic Monthly, July 1945, pp 101-108.",{"_31":12250,"_33":12251},[],{"_35":160,"_37":12252,"_39":744,"_41":12253,"_66":12254,"_68":12255,"_70":69},"Fh_lGnxZ",{},[],"[Colson & Hall 1990] F. Colson & W. Hall, \"Prologue to Partition: Viceroy Mountabatten and the Handling of the INA Crisis\", to be published in the J. of theAssociationofHistoryandComputing, Autumn1990.",{"_31":12257,"_33":12258},[],{"_35":160,"_37":12259,"_39":744,"_41":12260,"_66":12261,"_68":12262,"_70":69},"6pZh82Vf",{},[],"[Davis & Heath 1989] H. Davis & I. Heath, \"An Evaluation of Actor for Developing Large Windows Applications\", Department of Electronics and Computer Science CSTR 89-5, University of Southampton, 1989.",{"_31":12264,"_33":12265},[],{"_35":160,"_37":12266,"_39":744,"_41":12267,"_66":12268,"_68":12269,"_70":69},"4AWBFAj1",{},[],"[Delisle 1987] N. Delisle & M. Schwartz, \"Contexts - A Partitioning Concept for Hypertext\", J.of the ACM Transactions on Office Information Systems, Vol. 5, No. 2, April 1987, pp 168-186.",{"_31":12271,"_33":12272},[],{"_35":160,"_37":12273,"_39":744,"_41":12274,"_66":12275,"_68":12276,"_70":69},"4t1Zoa_P",{},[],"[Englebart 1963] D.C. ENGELBART, \"A Conceptual Framework for the Augmentation of Man's Intellect\", in Vistas in Information Handling, Vol.l, Spartan Books, London, 1963.",{"_31":12278,"_33":12279},[],{"_35":160,"_37":12280,"_39":744,"_41":12281,"_66":12282,"_68":12283,"_70":69},"5yiI4lG1",{},[],"[Furuta et al. 1989] R. Furuta, C. Plaisant, & B. Shneiderman, \"A Spectrum of Automatic Hypertext Constructs\", J. ofHypermedia, Vol. 1, No. 2, 1989, pp 179- 195.",{"_31":12285,"_33":12286},[],{"_35":160,"_37":12287,"_39":744,"_41":12288,"_66":12289,"_68":12290,"_70":69},"MdszdabQ",{},[],"[Halasz 1988] F.G. Halasz, \"Reflections on Notecards: Seven Issues for the Next Generation of Hypermedia Systems\", Communications of the ACM, 31(7), July 1988, pp 836-852.",{"_31":12292,"_33":12293},[],{"_35":160,"_37":12294,"_39":744,"_41":12295,"_66":12296,"_68":12297,"_70":69},"XCgeHLuP",{},[],"[Nelson 1967] T.H. Nelson, \"Getting It Out of Our System\", in Schechter G. (ed.) Information Retrieval: A Critical Review, Thompson Books, Wash. D.C., 1967.",{"_31":12299,"_33":12300},[],{"_35":160,"_37":12301,"_39":744,"_41":12302,"_66":12303,"_68":12304,"_70":69},"pZPB2gw4",{},[],"[Nielsen 1990a] J. NIELSEN, \"The Art of Navigating Through Hypertext\", Communications ofthe ACM, 33(3), March 1990, pp 297-310.",{"_31":12306,"_33":12307},[],{"_35":160,"_37":12308,"_39":744,"_41":12309,"_66":12310,"_68":12311,"_70":69},"evR1RJrJ",{},[],"[Nielsen 1990b] J. NIELSEN, Hypertext and Hypermedia, Academic Press, 1990. [Rahtz 1989a] S. Rahtz, L. Carr & W. Hall, \"New designs for Archaeological",{"_31":12313,"_33":12314},[],{"_35":160,"_37":12315,"_39":744,"_41":12316,"_66":12317,"_68":12318,"_70":69},"gq-ugXJH",{},[],"Reports\", Science and Archaeology, no. 31, 1989, pp 20-34.",{"_31":12320,"_33":12321},[],{"_35":160,"_37":12322,"_39":744,"_41":12323,"_66":12324,"_68":12325,"_70":69},"O5sGpHkx",{},[],"[Rahtz 1989b] S. Rahtz, L. Carr, & W. Hall, \"Creating Multimedia Documents\",",{"_31":12327,"_33":12328},[],{"_35":160,"_37":12329,"_39":744,"_41":12330,"_66":12331,"_68":12332,"_70":69},"v47uPZ-b",{},[],"in Hypertext: the State of the Art (ed. McAleese) Intellect Ltd, 1990.",{"_31":12334,"_33":12335},[],{"_35":160,"_37":12336,"_39":744,"_41":12337,"_66":12338,"_68":12339,"_70":69},"Xmu-awUK",{},[],"[Shneiderman 1987] B. Shneiderman, \"User Interface Design for the Hyperties Electronic Encyclopedia\", Proceedings of the ACM Hypertext'87 Conference, Chapel Hill, NC, November 1987, pp!89-194.",{"_31":12341,"_33":12342},[],{"_35":160,"_37":12343,"_39":744,"_41":12344,"_66":12345,"_68":12346,"_70":69},"bfx5yR_X",{},[],"[Shneiderman et al. 1989] B. SHNEIDERMAN, D. BRETHAUER, C. PLAISANT & R. Potter, \"The Hyperties Electronic Encyclopedia: An Evaluation Based on Three Museum Installations”, J. American Societyfor Information Science, 40 (3), May 1989, ppi72-182.",{"_31":12348,"_33":12349},[],{"_35":160,"_37":12350,"_39":744,"_41":12351,"_66":12352,"_68":12353,"_70":69},"tLo5UMhK",{},[],"[Shneiderman & Kearsley 1989] B. Shneiderman & G. Kearsley, Hypertext Hands On, Addison-Wesley, 1989.",{"_31":12355,"_33":12356},[],{"_35":160,"_37":12357,"_39":744,"_41":12358,"_66":12359,"_68":12360,"_70":69},"k4egv8uy",{},[],"[Yankelovich et al 1985] N. Yankelovich, N. Meyrowitz & A. VAN Dam, \"Reading and Writing the Electronic Book”, IEEE Computer, October 1985.",{"_31":12362,"_33":12363},[],{"_35":160,"_37":12364,"_39":744,"_41":12365,"_66":12366,"_68":12367,"_70":69},"A4WRp0sA",{},[],"[Yankelovich et al 1988] N. Yankelovich, B. Haan, N. Meyrowitz & S. Drucker, \"Intermedia: The Concept and Construction of a Seamless Information Environment\", IEEE Computer, January 1988, pp 81-96.",{"_35":870,"_37":12369,"_39":744,"_41":12370,"_66":12371,"_68":3495,"_70":69},"iFOjUDyH",{"_273":323},[],[53],"/records/microcosm-an-open-model-for-hypermedia-with-dynamic-linking",{"_82":764},{},{"_37":741,"_95":53,"_54":12377,"_71":744,"_97":-5,"_98":-5,"_99":-5,"_100":-5,"_94":6},[55,743],1772031973289,[149,741,744],"[\"ENTITY\",\"hm://z6MkrvYZzMYaCxyjbFWsZicdPCrcVmiXvgeY3i65GERQjjoH/records/microcosm-an-open-model-for-hypermedia-with-dynamic-linking\",\"bafy2bzacedslgk3murmoxfmfgbz43t6hgjml4f4ngzhztmufodoglys4tus46\"]",{"_110":12382,"_147":12440,"_150":12441},{"_112":12383,"_131":132,"_133":12439,"_135":-5,"_136":137,"_138":137,"_139":137,"_140":-5,"_141":-5,"_142":62,"_143":144,"_145":146},{"_35":26,"_26":12384,"_37":12437},{"_28":12385,"_71":770,"_72":53,"_73":12433,"_54":12434,"_76":777,"_78":777,"_80":12435,"_84":12436,"_86":770,"_88":89},[12386,12393,12404,12415],{"_31":12387,"_33":12388},[],{"_35":160,"_37":12389,"_39":770,"_41":12390,"_66":12391,"_68":12392,"_70":69},"5LlAEp9Z",{},[],"Mark S. Miller1, Tom Van Cutsem2, and Bill Tulloh",{"_31":12394,"_33":12395},[],{"_35":160,"_37":12396,"_39":770,"_41":12397,"_66":12398,"_68":12403,"_70":69},"tujwccLO",{},[12399],{"_35":166,"_167":12400,"_169":12401,"_41":12402,"_70":69},[137],[240],{},"Abstract. Contracts enable mutually suspicious parties to cooperate safely through the exchange of rights. Smart contracts are programs whose behavior enforces the terms of the contract. This paper shows how such contracts can be specified elegantly and executed safely, given an appropriate distributed, secure, persistent, and ubiquitous computational fabric. JavaScript provides the ubiquity but must be significantly extended to deal with the other aspects. The first part of this paper is a progress report on our efforts to turn JavaScript into this fabric. To demonstrate the suitability of this design, we describe an escrow exchange contract implemented in 42 lines of JavaScript code.",{"_31":12405,"_33":12406},[],{"_35":160,"_37":12407,"_39":770,"_41":12408,"_66":12409,"_68":12414,"_70":69},"6KUzV1Qy",{},[12410],{"_35":166,"_167":12411,"_169":12412,"_41":12413,"_70":69},[137],[240],{},"Keywords: security, distributed objects, object-capabilities, smart contracts.",{"_31":12416,"_33":12424},[12417],{"_31":12418,"_33":12419},[],{"_35":160,"_37":12420,"_39":770,"_41":12421,"_66":12422,"_68":12423,"_70":69},"NBw2Rxx_",{},[],"The fabric of the global economy is held together by contracts. A contract is an agreed framework for the rearrangement of rights between mutually suspicious parties. But existing contracts are ambiguous, jurisdictions-specific, and written, interpreted, and adjudicated only by expensive experts. Smart contracts are contract-like arrangements expressed in program code, where the behavior of the program enforces the terms of the “contract”[1]. Though not a substitute for legal contracts, they can provide some of the benefits of contracts for fine-grain, jurisdiction-free, and automated arrangements for which legal contracts are impractical. To realize this potential, smart contracts need a distributed, secure, persistent, and ubiquitous computational fabric. To avoid merely substituting one set of expensive experts for another, non-experts should be able to write smart contracts understandable by other non-experts. We1 are working towards turning JavaScript into such a fabric. JavaScript is already understood and used by many non-expert programmers. We call our target JavaScript platform Dr. SES for Distributed Resilient Secure EcmaScript. 2 Dr. SES is not specifically tied to electronic rights (erights) or smart contracts per se. Its focus is to make distributed secure programming in JavaScript as effortless as possible. But much of the design of Dr. SES and its predecessors [2,3,4] was shaped by examining what we need to express smart contracts simply. Taking a rights-based approach to local and distributed computing, we believe, has led us to building a better general purpose platform as well as one naturally suited for expressing new kinds of erights and contracts.",{"_35":160,"_37":12425,"_39":770,"_41":12426,"_66":12427,"_68":12432,"_70":69},"V4liDAZK",{"_273":323},[12428],{"_35":166,"_167":12429,"_169":12430,"_41":12431,"_70":69},[137],[2477],{},"Smart Contracts for the Rest of 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